Far infrared spectra of solid state aliphatic amino acids in different protonation states

Far infrared speca of solid state aliphatic amino acids in different protonation states Aurélien Trivella 1, Thomas Gaillard 2,3, Roland H. Stote 2,4 Pea Hellwig 1, January 29, 2010 Supporting Information 1 Institut de Chimie, UMR 7177, Laboratoire de specoscopie vibrationnelle et élecochimie des biomolécules, Université de Sasbourg, 1 rue Blaise Pascal, F-67070 Sasbourg 2 Institut de Chimie, UMR 7177, Laboratoire de biophysicochimie moléculaire, Université de Sasbourg, 4 rue Blaise Pascal, F-67070 Sasbourg 3 Current address: Laboratoire de Biochimie (CNRS UMR7654), Department of Biology, Ecole Polytechnique, 91128 Palaiseau, France. 4 Current address: Biocomputing Group, Suctural Biology and Genomics Department, Institut de Génétique et de Biologie Moléculaire et Cellulaire, 1 rue Laurent Fries, BP 10142, 67404 Illkirch CEDEX, France. Corresponding author: hellwig@chimie.u-sasbg.fr both authors conibuted equally to this work 1

(a) Glycine beta (b) Glycine alpha (c) Glycine cation (d) Glycine anion Figure S1: Geomey of optimized suctures. Glycine β zwitterion (a), glycine α zwitterion (b), glycine cation (c), glycine anion (d). Ball and stick representation with hydrogen, carbon, niogen, oxygen, and other atoms in white, light blue, dark blue, red, and green, respectively. Molecules represented have their Cα atom inside the unit cell. Intermolecular polar contacts are indicated with an orange dashed line. Atom names for one molecule and unit cell axes are labelled. 2

(e) L-Alanine (f) L-Valine (g) L-Leucine (h) L-Isoleucine Figure S1: (continued) Geomey of optimized suctures. L-alanine (e), L-valine (f), L-leucine (g), L-isoleucine (h). Ball and stick representation with hydrogen, carbon, niogen, oxygen, and other atoms in white, light blue, dark blue, red, and green, respectively. Molecules represented have their Cα atom inside the unit cell. Intermolecular polar contacts are indicated with an orange dashed line. Atom names for one molecule and unit cell axes are labelled. 3

Table S1: Crystal system, space group, number of atoms per molecule, number of molecules per asymmeic unit, number of molecules per unit cell, number of normal modes, irreducible group representations, and symmey of acoustic modes. at./ mol./ mol./ acoustic modes molecule system group mol. asym. cell modes irreps x y z glycine β monoclinic P2 1 (4) 10 1 2 60 A,B B B A glycine α monoclinic P2 1 /n (14) 10 1 4 120 Ag,Bg,Au,Bu Bu Bu Au glycinium,cl monoclinic P2 1 /n (14) 12 1 4 144 Ag,Bg,Au,Bu Bu Bu Au glycinate,na + orthorhombic P2 1 2 1 2 1 (19) 10 1 4 120 A,B1,B2,B3 B1 B2 B3 L-alanine orthorhombic P2 1 2 1 2 1 (19) 13 1 4 156 A,B1,B2,B3 B1 B2 B3 L-valine monoclinic P2 1 (4) 19 2 4 228 A,B B B A L-leucine monoclinic P2 1 (4) 22 2 4 264 A,B B B A L-isoleucine monoclinic P2 1 (4) 22 2 4 264 A,B B B A 4

Table S2: Symmeized Pulay coordinates for glycine zwitterion number a coordinate b symbol c description 1 b N,Cα ν(ncα) NCα setch. 2 b Cα,C ν(cαc) CαC setch. 3 b C,O1 ν(co 2 ) CO 2 setch. 4 b C,O2 ν(co 2 ) CO 2 setch. 5 b Cα,Hα1 +b Cα,Hα2 ν s(cαh 2 ) CαH 2 sym. setch. 6 b Cα,Hα1 b Cα,Hα2 ν a(cαh 2 ) CαH 2 asym. setch. 7 b N,H1 ν(nh + 3 ) NH + 3 setch. 8 b N,H2 ν(nh + 3 ) NH + 3 setch. 9 b N,H3 ν(nh + 3 ) NH + 3 setch. 10 2a O1,C,O2 a Cα,C,O1 a Cα,C,O2 δ(co 2 ) CO 2 scissoring 11 a Cα,C,O1 a Cα,C,O2 ρ(co 2 ) CO 2 rocking 12 i O1,Cα,C,O2 ω(co 2 ) CO 2 wagging 13 5a Hα1,Cα,Hα2 a N,Cα,C δ(cαh 2 ) CαH 2 scissoring 14 5a N,Cα,C a Hα1,Cα,Hα2 δ(ncαc) NCαC scissoring 15 a Hα1,Cα,C a Hα2,Cα,C +a N,Cα,Hα1 a N,Cα,Hα2 ρ(cαh 2 ) CαH 2 rocking 16 a Hα1,Cα,C +a Hα2,Cα,C a N,Cα,Hα1 a N,Cα,Hα2 ω(cαh 2 ) CαH 2 wagging 17 a Hα1,Cα,C a Hα2,Cα,C a N,Cα,Hα1 +a N,Cα,Hα2 t(cαh 2 ) CαH 2 twisting 18 a H1,N,H2 +a H1,N,H3 +a H2,N,H3 δ s(nh + 3 ) NH + 3 sym. def. a H1,N,Cα a H2,N,Cα a H3,N,Cα 19 2a H2,N,H3 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 20 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 21 2a H1,N,Cα a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 22 a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 23 d x,n,cα,x τ(nh + 3 ) NH + 3 torsion 24 d x,cα,c,x τ(co 2 ) CO 2 torsion a arbiary numbering b b: bond, a: angle, d: dihedral, i: improper dihedral. Normalization factors are omitted and correspond to ( P c 2 i )1/2 c ν: setching, δ: bending, ρ: rocking, t: twisting, ω: wagging, τ: torsion 5

Table S3: Symmeized Pulay coordinates for glycine cation number a coordinate b symbol c description 1 b N,Cα ν(ncα) NCα setch. 2 b Cα,C ν(cαc) CαC setch. 3 b C,O1 ν(co 2 ) CO 2 setch. 4 b C,O2 ν(co 2 ) CO 2 setch. 5 b Cα,Hα1 +b Cα,Hα2 ν s(cαh 2 ) CαH 2 sym. setch. 6 b Cα,Hα1 b Cα,Hα2 ν a(cαh 2 ) CαH 2 asym. setch. 7 b N,H1 ν(nh + 3 ) NH + 3 setch. 8 b N,H2 ν(nh + 3 ) NH + 3 setch. 9 b N,H3 ν(nh + 3 ) NH + 3 setch. 10 2a O1,C,O2 a Cα,C,O1 a Cα,C,O2 δ(co 2 H) CO 2 H scissoring 11 a Cα,C,O1 a Cα,C,O2 ρ(co 2 H) CO 2 H rocking 12 i O1,Cα,C,O2 ω(co 2 H) CO 2 H wagging 13 5a Hα1,Cα,Hα2 a N,Cα,C δ(cαh 2 ) CαH 2 scissoring 14 5a N,Cα,C a Hα1,Cα,Hα2 δ(ncαc) NCαC scissoring 15 a Hα1,Cα,C a Hα2,Cα,C +a N,Cα,Hα1 a N,Cα,Hα2 ρ(cαh 2 ) CαH 2 rocking 16 a Hα1,Cα,C +a Hα2,Cα,C a N,Cα,Hα1 a N,Cα,Hα2 ω(cαh 2 ) CαH 2 wagging 17 a Hα1,Cα,C a Hα2,Cα,C a N,Cα,Hα1 +a N,Cα,Hα2 t(cαh 2 ) CαH 2 twisting 18 a H1,N,H2 +a H1,N,H3 +a H2,N,H3 δ s(nh + 3 ) NH + 3 sym. def. a H1,N,Cα a H2,N,Cα a H3,N,Cα 19 2a H2,N,H3 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 20 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 21 2a H1,N,Cα a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 22 a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 23 d x,n,cα,x τ(nh + 3 ) NH + 3 torsion 24 d x,cα,c,x τ(co 2 H) CO 2 H torsion 25 b O2,HO2 ν(oh) OH setch. 26 a C,O2,HO2 δ(coh) COH def. 27 d x,c,o2,x τ(co) CO torsion 28 b Cl,H1 +b Cl,H3 ν s(cl HN) Cl HN sym. setch. 29 b Cl,H1 b Cl,H3 ν a(cl HN) Cl HN asym. setch. 30 b Cl,HO2 ν(cl HO) Cl HO setch. a arbiary numbering b b: bond, a: angle, d: dihedral, i: improper dihedral. Normalization factors are omitted and correspond to ( P c 2 i )1/2 c ν: setching, δ: bending, ρ: rocking, t: twisting, ω: wagging, τ: torsion 6

Table S4: Symmeized Pulay coordinates for glycine anion number a coordinate b symbol c description 1 b N,Cα ν(ncα) NCα setch. 2 b Cα,C ν(cαc) CαC setch. 3 b C,O1 ν(co 2 ) CO 2 setch. 4 b C,O2 ν(co 2 ) CO 2 setch. 5 b Cα,Hα1 +b Cα,Hα2 ν s(cαh 2 ) CαH 2 sym. setch. 6 b Cα,Hα1 b Cα,Hα2 ν a(cαh 2 ) CαH 2 asym. setch. 7 b N,H1 ν(nh 2 ) NH 2 setch. 8 b N,H2 ν(nh 2 ) NH 2 setch. 9 2a O1,C,O2 a Cα,C,O1 a Cα,C,O2 δ(co 2 ) CO 2 scissoring 10 a Cα,C,O1 a Cα,C,O2 ρ(co 2 ) CO 2 rocking 11 i O1,Cα,C,O2 ω(co 2 ) CO 2 wagging 12 5a Hα1,Cα,Hα2 a N,Cα,C δ(cαh 2 ) CαH 2 scissoring 13 5a N,Cα,C a Hα1,Cα,Hα2 δ(ncαc) NCαC scissoring 14 a Hα1,Cα,C a Hα2,Cα,C +a N,Cα,Hα1 a N,Cα,Hα2 ρ(cαh 2 ) CαH 2 rocking 15 a Hα1,Cα,C +a Hα2,Cα,C a N,Cα,Hα1 a N,Cα,Hα2 ω(cαh 2 ) CαH 2 wagging 16 a Hα1,Cα,C a Hα2,Cα,C a N,Cα,Hα1 +a N,Cα,Hα2 t(cαh 2 ) CαH 2 twisting 17 2a H1,N,H2 a Cα,N,H1 a Cα,N,H2 δ(nh 2 ) NH 2 scissoring 18 a Cα,N,H1 a Cα,N,H2 ρ(nh 2 ) NH 2 rocking 19 i H1,Cα,N,H2 ω(nh 2 ) NH 2 wagging 20 d x,n,cα,x τ(nh 2 ) NH 2 torsion 21 d x,cα,c,x τ(co 2 ) CO 2 torsion 22 b O2,Na ν(ona + ) ONa + setch. 23 a C,O2,Na δ(cona + ) CONa + def. 24 d x,c,o2,x τ(cona + ) xcona + torsion a arbiary numbering b b: bond, a: angle, d: dihedral, i: improper dihedral. Normalization factors are omitted and correspond to ( P c 2 i )1/2 c ν: setching, δ: bending, ρ: rocking, t: twisting, ω: wagging, τ: torsion 7

Table S5: Symmeized Pulay coordinates for L-alanine zwitterion number a coordinate b symbol c description 1 b N,Cα ν(ncα) NCα setch. 2 b Cα,C ν(cαc) CαC setch. 3 b Cα,Cβ ν(cαcβ) CαCβ setch. 4 b C,O1 ν(co 2 ) CO 2 setch. 5 b C,O2 ν(co 2 ) CO 2 setch. 6 b Cα,Hα ν(cαh) CαH setch. 7 b N,H1 ν(nh + 3 ) NH + 3 setch. 8 b N,H2 ν(nh + 3 ) NH + 3 setch. 9 b N,H3 ν(nh + 3 ) NH + 3 setch. 10 b Cβ,Hβ1 +b Cβ,Hβ2 +b Cβ,Hβ3 ν s(cβh 3 ) CβH 3 sym. setch. 11 2b Cβ,Hβ1 b Cβ,Hβ2 b Cβ,Hβ3 ν a(cβh 3 ) CβH 3 asym. setch. 12 b Cβ,Hβ2 b Cβ,Hβ3 ν a(cβh 3 ) CβH 3 asym. setch. 13 2a O1,C,O2 a Cα,C,O1 a Cα,C,O2 δ(co 2 ) CO 2 scissoring 14 a Cα,C,O1 a Cα,C,O2 ρ(co 2 ) CO 2 rocking 15 i O1,Cα,C,O2 ω(co 2 ) CO 2 wagging 16 2a C,Cα,Hα a N,Cα,Hα a Cβ,Cα,Hα ρ(cαh) CαH rocking 17 a N,Cα,Hα a Cβ,Cα,Hα ρ(cαh) CαH rocking 18 4a C,Cα,N +a C,Cα,Cβ +a Cβ,Cα,N δ(ncαc) NCαC def. 19 4a C,Cα,Cβ +a Cβ,Cα,N +a C,Cα,N δ(ccαcβ) CCαCβ def. 20 4a Cβ,Cα,N +a C,Cα,N +a C,Cα,Cβ δ(ncαcβ) NCαCβ def. 21 a H1,N,H2 +a H1,N,H3 +a H2,N,H3 δ s(nh + 3 ) NH + 3 sym. def. a H1,N,Cα a H2,N,Cα a H3,N,Cα 22 2a H2,N,H3 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 23 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 24 2a H1,N,Cα a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 25 a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 26 a Hβ1,Cβ,Hβ2 +a Hβ1,Cβ,Hβ3 +a Hβ2,Cβ,Hβ3 δ s(cβh 3 ) CβH 3 sym. def. a Hβ1,Cβ,Cα a Hβ2,Cβ,Cα a Hβ3,Cβ,Cα 27 2a Hβ2,Cβ,Hβ3 a Hβ1,Cβ,Hβ2 a Hβ1,Cβ,Hβ3 δ a(cβh 3 ) CβH 3 asym. def. 28 a Hβ1,Cβ,Hβ2 a Hβ1,Cβ,Hβ3 δ a(cβh 3 ) CβH 3 asym. def. 29 2a Hβ3,Cβ,Cα a Hβ1,Cβ,Cα a Hβ2,Cβ,Cα ρ(cβh 3 ) CβH 3 rocking 30 a Hβ1,Cβ,Cα a Hβ2,Cβ,Cα ρ(cβh 3 ) CβH 3 rocking 31 d x,n,cα,x τ(nh + 3 ) NH + 3 torsion 32 d x,cα,c,x τ(co 2 ) CO 2 torsion 33 d x,cα,cβ,x τ(cβh 3 ) CβH 3 torsion a arbiary numbering b b: bond, a: angle, d: dihedral, i: improper dihedral. Normalization factors are omitted and correspond to ( P c 2 i )1/2 c ν: setching, δ: bending, ρ: rocking, t: twisting, ω: wagging, τ: torsion 8

Table S6: Symmeized Pulay coordinates for L-valine zwitterion number a coordinate b symbol c description 1 b N,Cα ν(ncα) NCα setch. 2 b Cα,C ν(cαc) CαC setch. 3 b Cα,Cβ ν(cαcβ) CαCβ setch. 4 b Cβ,Cγ1 ν(cβcγ) CβCγ setch. 5 b Cβ,Cγ2 ν(cβcγ) CβCγ setch. 6 b C,O1 ν(co 2 ) CO 2 setch. 7 b C,O2 ν(co 2 ) CO 2 setch. 8 b Cα,Hα ν(cαh) CαH setch. 9 b Cβ,Hβ ν(cβh) CβH setch. 10 b N,H1 ν(nh + 3 ) NH + 3 setch. 11 b N,H2 ν(nh + 3 ) NH + 3 setch. 12 b N,H3 ν(nh + 3 ) NH + 3 setch. 13 b Cγ1,Hγ11 +b Cγ1,Hγ12 +b Cγ1,Hγ13 ν s(cγh 3 ) CγH 3 sym. setch. 14 2b Cγ1,Hγ11 b Cγ1,Hγ12 b Cγ1,Hγ13 ν a(cγh 3 ) CγH 3 asym. setch. 15 b Cγ1,Hγ12 b Cγ1,Hγ13 ν a(cγh 3 ) CγH 3 asym. setch. 16 b Cγ2,Hγ21 +b Cγ2,Hγ22 +b Cγ2,Hγ23 ν s(cγh 3 ) CγH 3 sym. setch. 17 2b Cγ2,Hγ21 b Cγ2,Hγ22 b Cγ2,Hγ23 ν a(cγh 3 ) CγH 3 asym. setch. 18 b Cγ2,Hγ22 b Cγ2,Hγ23 ν a(cγh 3 ) CγH 3 asym. setch. 19 2a O1,C,O2 a Cα,C,O1 a Cα,C,O2 δ(co 2 ) CO 2 scissoring 20 a Cα,C,O1 a Cα,C,O2 ρ(co 2 ) CO 2 rocking 21 i O1,Cα,C,O2 ω(co 2 ) CO 2 wagging 22 2a C,Cα,Hα a N,Cα,Hα a Cβ,Cα,Hα ρ(cαh) CαH rocking 23 a N,Cα,Hα a Cβ,Cα,Hα ρ(cαh) CαH rocking 24 4a C,Cα,N +a C,Cα,Cβ +a Cβ,Cα,N δ(ncαc) NCαC def. 25 4a C,Cα,Cβ +a Cβ,Cα,N +a C,Cα,N δ(ccαcβ) CCαCβ def. 26 4a Cβ,Cα,N +a C,Cα,N +a C,Cα,Cβ δ(ncαcβ) NCαCβ def. 27 2a Cα,Cβ,Hβ a Cγ1,Cβ,Hβ a Cγ2,Cβ,Hβ ρ(cβh) CβH rocking 28 a Cγ1,Cβ,Hβ a Cγ2,Cβ,Hβ ρ(cβh) CβH rocking 29 4a Cγ1,Cβ,Cγ2 +a Cγ1,Cβ,Cα +a Cγ2,Cβ,Cα δ(cγcβcγ) CγCβCγ def. 30 4a Cγ1,Cβ,Cα +a Cγ2,Cβ,Cα +a Cγ1,Cβ,Cγ2 δ(cαcβcγ) CαCβCγ def. 31 4a Cγ2,Cβ,Cα +a Cγ1,Cβ,Cγ2 +a Cγ1,Cβ,Cα δ(cαcβcγ) CαCβCγ def. 32 a H1,N,H2 +a H1,N,H3 +a H2,N,H3 δ s(nh + 3 ) NH + 3 sym. def. a H1,N,Cα a H2,N,Cα a H3,N,Cα 33 2a H2,N,H3 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 34 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 35 2a H1,N,Cα a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 36 a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 37 a Hγ11,Cγ1,Hγ12 +a Hγ11,Cγ1,Hγ13 +a Hγ12,Cγ1,Hγ13 δ s(cγh 3 ) CγH 3 sym. def. a Hγ11,Cγ1,Cβ a Hγ12,Cγ1,Cβ a Hγ13,Cγ1,Cβ 38 2a Hγ12,Cγ1,Hγ13 a Hγ11,Cγ1,Hγ12 a Hγ11,Cγ1,Hγ13 δ a(cγh 3 ) CγH 3 asym. def. 39 a Hγ11,Cγ1,Hγ12 a Hγ11,Cγ1,Hγ13 δ a(cγh 3 ) CγH 3 asym. def. 40 2a Hγ11,Cγ1,Cβ a Hγ12,Cγ1,Cβ a Hγ13,Cγ1,Cβ ρ(cγh 3 ) CγH 3 rocking 41 a Hγ12,Cγ1,Cβ a Hγ13,Cγ1,Cβ ρ(cγh 3 ) CγH 3 rocking 42 a Hγ21,Cγ2,Hγ22 +a Hγ21,Cγ2,Hγ23 +a Hγ22,Cγ2,Hγ23 δ s(cγh 3 ) CγH 3 sym. def. a Hγ21,Cγ2,Cβ a Hγ22,Cγ2,Cβ a Hγ23,Cγ2,Cβ 43 2a Hγ22,Cγ2,Hγ23 a Hγ21,Cγ2,Hγ22 a Hγ21,Cγ2,Hγ23 δ a(cγh 3 ) CγH 3 asym. def. 44 a Hγ21,Cγ2,Hγ22 a Hγ21,Cγ2,Hγ23 δ a(cγh 3 ) CγH 3 asym. def. 45 2a Hγ21,Cγ2,Cβ a Hγ22,Cγ2,Cβ a Hγ23,Cγ2,Cβ ρ(cγh 3 ) CγH 3 rocking 46 a Hγ22,Cγ2,Cβ a Hγ23,Cγ2,Cβ ρ(cγh 3 ) CγH 3 rocking 47 d x,n,cα,x τ(nh + 3 ) NH + 3 torsion 48 d x,cα,c,x τ(co 2 ) CO 2 torsion 49 d x,cα,cβ,x τ(cαcβ) CαCβ torsion 50 d x,cβ,cγ1,x τ(cγh 3 ) CγH 3 torsion 51 d x,cβ,cγ2,x τ(cγh 3 ) CγH 3 torsion a arbiary numbering b b: bond, a: angle, d: dihedral, i: improper dihedral. Normalization factors are omitted and correspond to ( P c 2 i )1/2 c ν: setching, δ: bending, ρ: rocking, t: twisting, ω: wagging, τ: torsion 9

Table S7: Symmeized Pulay coordinates for L-leucine zwitterion number a coordinate b symbol c description 1 b N,Cα ν(ncα) NCα setch. 2 b Cα,C ν(cαc) CαC setch. 3 b Cα,Cβ ν(cαcβ) CαCβ setch. 4 b Cβ,Cγ ν(cβcγ) CβCγ setch. 5 b Cγ,Cδ1 ν(cγcδ) CγCδ setch. 6 b Cγ,Cδ2 ν(cγcδ) CγCδ setch. 7 b C,O1 ν(co 2 ) CO 2 setch. 8 b C,O2 ν(co 2 ) CO 2 setch. 9 b Cα,Hα ν(cαh) CαH setch. 10 b Cβ,Hβ1 +b Cβ,Hβ2 ν s(cβh 2 ) CβH 2 sym. setch. 11 b Cβ,Hβ1 b Cβ,Hβ2 ν a(cβh 2 ) CβH 2 asym. setch. 12 b Cγ,Hγ ν(cγh) CγH setch. 13 b N,H1 ν(nh + 3 ) NH + 3 setch. 14 b N,H2 ν(nh + 3 ) NH + 3 setch. 15 b N,H3 ν(nh + 3 ) NH + 3 setch. 16 b Cδ1,Hδ11 +b Cδ1,Hδ12 +b Cδ1,Hδ13 ν s(cδh 3 ) CδH 3 sym. setch. 17 2b Cδ1,Hδ11 b Cδ1,Hδ12 b Cδ1,Hδ13 ν a(cδh 3 ) CδH 3 asym. setch. 18 b Cδ1,Hδ12 b Cδ1,Hδ13 ν a(cδh 3 ) CδH 3 asym. setch. 19 b Cδ2,Hδ21 +b Cδ2,Hδ22 +b Cδ2,Hδ23 ν s(cδh 3 ) CδH 3 sym. setch. 20 2b Cδ2,Hδ21 b Cδ2,Hδ22 b Cδ2,Hδ23 ν a(cδh 3 ) CδH 3 asym. setch. 21 b Cδ2,Hδ22 b Cδ2,Hδ23 ν a(cδh 3 ) CδH 3 asym. setch. 22 2a O1,C,O2 a Cα,C,O1 a Cα,C,O2 δ(co 2 ) CO 2 scissoring 23 a Cα,C,O1 a Cα,C,O2 ρ(co 2 ) CO 2 rocking 24 i O1,Cα,C,O2 ω(co 2 ) CO 2 wagging 25 2a C,Cα,Hα a N,Cα,Hα a Cβ,Cα,Hα ρ(cαh) CαH rocking 26 a N,Cα,Hα a Cβ,Cα,Hα ρ(cαh) CαH rocking 27 4a C,Cα,N +a C,Cα,Cβ +a Cβ,Cα,N δ(ncαc) NCαC def. 28 4a C,Cα,Cβ +a Cβ,Cα,N +a C,Cα,N δ(ccαcβ) CCαCβ def. 29 4a Cβ,Cα,N +a C,Cα,N +a C,Cα,Cβ δ(ncαcβ) NCαCβ def. 30 5a Hβ1,Cβ,Hβ2 a Cα,Cβ,Cγ δ(cβh 2 ) CβH 2 scissoring 31 5a Cα,Cβ,Cγ a Hβ1,Cβ,Hβ2 δ(cαcβcγ) CαCβCγ scissoring 32 a Hβ1,Cβ,Cγ a Hβ2,Cβ,Cγ +a Cα,Cβ,Hβ1 a Cα,Cβ,Hβ2 ρ(cβh 2 ) CβH 2 rocking 33 a Hβ1,Cβ,Cγ +a Hβ2,Cβ,Cγ a Cα,Cβ,Hβ1 a Cα,Cβ,Hβ2 ω(cβh 2 ) CβH 2 wagging 34 a Hβ1,Cβ,Cγ a Hβ2,Cβ,Cγ a Cα,Cβ,Hβ1 +a Cα,Cβ,Hβ2 t(cβh 2 ) CβH 2 twisting 35 2a Cβ,Cγ,Hγ a Cδ1,Cγ,Hγ a Cδ2,Cγ,Hγ ρ(cγh) CγH rocking 36 a Cδ1,Cγ,Hγ a Cδ2,Cγ,Hγ ρ(cγh) CγH rocking 37 4a Cδ1,Cγ,Cδ2 +a Cδ1,Cγ,Cβ +a Cδ2,Cγ,Cβ δ(cδcγcδ) CδCγCδ def. 38 4a Cδ1,Cγ,Cβ +a Cδ2,Cγ,Cβ +a Cδ1,Cγ,Cδ2 δ(cβcγcδ) CβCγCδ def. 39 4a Cδ2,Cγ,Cβ +a Cδ1,Cγ,Cδ2 +a Cδ1,Cγ,Cβ δ(cβcγcδ) CβCγCδ def. 40 a H1,N,H2 +a H1,N,H3 +a H2,N,H3 δ s(nh + 3 ) NH + 3 sym. def. a H1,N,Cα a H2,N,Cα a H3,N,Cα 41 2a H2,N,H3 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 42 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 43 2a H1,N,Cα a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 44 a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 45 a Hδ11,Cδ1,Hδ12 +a Hδ11,Cδ1,Hδ13 +a Hδ12,Cδ1,Hδ13 δ s(cδh 3 ) CδH 3 sym. def. a Hδ11,Cδ1,Cγ a Hδ12,Cδ1,Cγ a Hδ13,Cδ1,Cγ 46 2a Hδ12,Cδ1,Hδ13 a Hδ11,Cδ1,Hδ12 a Hδ11,Cδ1,Hδ13 δ a(cδh 3 ) CδH 3 asym. def. 47 a Hδ11,Cδ1,Hδ12 a Hδ11,Cδ1,Hδ13 δ a(cδh 3 ) CδH 3 asym. def. 48 2a Hδ11,Cδ1,Cγ a Hδ12,Cδ1,Cγ a Hδ13,Cδ1,Cγ ρ(cδh 3 ) CδH 3 rocking 49 a Hδ12,Cδ1,Cγ a Hδ13,Cδ1,Cγ ρ(cδh 3 ) CδH 3 rocking 50 a Hδ21,Cδ2,Hδ22 +a Hδ21,Cδ2,Hδ23 +a Hδ22,Cδ2,Hδ23 δ s(cδh 3 ) CδH 3 sym. def. a Hδ21,Cδ2,Cγ a Hδ22,Cδ2,Cγ a Hδ23,Cδ2,Cγ 51 2a Hδ22,Cδ2,Hδ23 a Hδ21,Cδ2,Hδ22 a Hδ21,Cδ2,Hδ23 δ a(cδh 3 ) CδH 3 asym. def. 52 a Hδ21,Cδ2,Hδ22 a Hδ21,Cδ2,Hδ23 δ a(cδh 3 ) CδH 3 asym. def. 53 2a Hδ21,Cδ2,Cγ a Hδ22,Cδ2,Cγ a Hδ23,Cδ2,Cγ ρ(cδh 3 ) CδH 3 rocking 54 a Hδ22,Cδ2,Cγ a Hδ23,Cδ2,Cγ ρ(cδh 3 ) CδH 3 rocking 55 d x,n,cα,x τ(nh + 3 ) NH + 3 torsion 56 d x,cα,c,x τ(co 2 ) CO 2 torsion 57 d x,cα,cβ,x τ(cαcβ) CαCβ torsion 58 d x,cβ,cγ,x τ(cβcγ) CβCγ torsion 59 d x,cγ,cδ1,x τ(cδh 3 ) CδH 3 torsion 60 d x,cγ,cδ2,x τ(cδh 3 ) CδH 3 torsion a arbiary numbering b b: bond, a: angle, d: dihedral, i: improper dihedral. Normalization factors are omitted and correspond to ( P c 2 i )1/2 c ν: setching, δ: bending, ρ: rocking, t: twisting, ω: wagging, τ: torsion 10

Table S8: Symmeized Pulay coordinates for L-isoleucine zwitterion number a coordinate b symbol c description 1 b N,Cα ν(ncα) NCα setch. 2 b Cα,C ν(cαc) CαC setch. 3 b Cα,Cβ ν(cαcβ) CαCβ setch. 4 b Cβ,Cγ1 ν(cβcγ1) CβCγ1 setch. 5 b Cβ,Cγ2 ν(cβcγ2) CβCγ2 setch. 6 b Cγ1,Cδ ν(cγ1cδ) Cγ1Cδ setch. 7 b C,O1 ν(co 2 ) CO 2 setch. 8 b C,O2 ν(co 2 ) CO 2 setch. 9 b Cα,Hα ν(cαh) CαH setch. 10 b Cβ,Hβ ν(cβh) CβH setch. 11 b Cγ1,Hγ11 +b Cγ1,Hγ12 ν s(cγh 2 ) Cγ1H 2 asym. setch. 12 b Cγ1,Hγ11 b Cγ1,Hγ12 ν a(cγh 2 ) Cγ1H 2 sym. setch. 13 b N,H1 ν(nh + 3 ) NH + 3 setch. 14 b N,H2 ν(nh + 3 ) NH + 3 setch. 15 b N,H3 ν(nh + 3 ) NH + 3 setch. 16 b Cγ2,Hγ21 +b Cγ2,Hγ22 +b Cγ2,Hγ23 ν s(cγh 3 ) Cγ2H 3 sym. setch. 17 2b Cγ2,Hγ21 b Cγ2,Hγ22 b Cγ2,Hγ23 ν a(cγh 3 ) Cγ2H 3 asym. setch. 18 b Cγ2,Hγ22 b Cγ2,Hγ23 ν a(cγh 3 ) Cγ2H 3 asym. setch. 19 b Cδ,Hδ1 +b Cδ,Hδ2 +b Cδ,Hδ3 ν s(cδh 3 ) CδH 3 sym. setch. 20 2b Cδ,Hδ1 b Cδ,Hδ2 b Cδ,Hδ3 ν a(cδh 3 ) CδH 3 asym. setch. 21 b Cδ,Hδ2 b Cδ,Hδ3 ν a(cδh 3 ) CδH 3 asym. setch. 22 2a O1,C,O2 a Cα,C,O1 a Cα,C,O2 δ(co 2 ) CO 2 scissoring 23 a Cα,C,O1 a Cα,C,O2 ρ(co 2 ) CO 2 rocking 24 i O1,Cα,C,O2 ω(co 2 ) CO 2 wagging 25 2a C,Cα,Hα a N,Cα,Hα a Cβ,Cα,Hα ρ(cαh) CαH rocking 26 a N,Cα,Hα a Cβ,Cα,Hα ρ(cαh) CαH rocking 27 4a C,Cα,N +a C,Cα,Cβ +a Cβ,Cα,N δ(ncαc) NCαC def. 28 4a C,Cα,Cβ +a Cβ,Cα,N +a C,Cα,N δ(ccαcβ) CCαCβ def. 29 4a Cβ,Cα,N +a C,Cα,N +a C,Cα,Cβ δ(ncαcβ) NCαCβ def. 30 2a Cα,Cβ,Hβ a Cγ1,Cβ,Hβ a Cγ2,Cβ,Hβ ρ(cβh) CβH rocking 31 a Cγ1,Cβ,Hβ a Cγ2,Cβ,Hβ ρ(cβh) CβH rocking 32 4a Cγ1,Cβ,Cγ2 +a Cγ1,Cβ,Cα +a Cγ2,Cβ,Cα δ(cγcβcγ) Cγ1CβCγ2 def. 33 4a Cγ1,Cβ,Cα +a Cγ2,Cβ,Cα +a Cγ1,Cβ,Cγ2 δ(cαcβcγ1) CαCβCγ1 def. 34 4a Cγ2,Cβ,Cα +a Cγ1,Cβ,Cγ2 +a Cγ1,Cβ,Cα δ(cαcβcγ2) CαCβCγ2 def. 35 5a Hγ11,Cγ1,Hγ12 a Cβ,Cγ1,Cδ δ(cγ1h 2 ) Cγ1H 2 scissoring 36 5a Cβ,Cγ1,Cδ a Hγ11,Cγ1,Hγ12 δ(cβcγ1cδ) CβCγ1Cδ scissoring 37 a Hγ11,Cγ1,Cδ a Hγ12,Cγ1,Cδ +a Cβ,Cγ1,Hγ11 a Cβ,Cγ1,Hγ12 ρ(cγ1h 2 ) Cγ1H 2 rocking 38 a Hγ11,Cγ1,Cδ +a Hγ12,Cγ1,Cδ a Cβ,Cγ1,Hγ11 a Cβ,Cγ1,Hγ12 ω(cγ1h 2 ) Cγ1H 2 wagging 39 a Hγ11,Cγ1,Cδ a Hγ12,Cγ1,Cδ a Cβ,Cγ1,Hγ11 +a Cβ,Cγ1,Hγ12 t(cγ1h 2 ) Cγ1H 2 twisting 40 a H1,N,H2 +a H1,N,H3 +a H2,N,H3 δ s(nh + 3 ) NH + 3 sym. def. a H1,N,Cα a H2,N,Cα a H3,N,Cα 41 2a H2,N,H3 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 42 a H1,N,H2 a H1,N,H3 δ a(nh + 3 ) NH + 3 asym. def. 43 2a H1,N,Cα a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 44 a H2,N,Cα a H3,N,Cα ρ(nh + 3 ) NH + 3 rocking 45 a Hγ21,Cγ2,Hγ22 +a Hγ21,Cγ2,Hγ23 +a Hγ22,Cγ2,Hγ23 δ s(cγh 3 ) Cγ2H 3 sym. def. a Hγ21,Cγ2,Cβ a Hγ22,Cγ2,Cβ a Hγ23,Cγ2,Cβ 46 2a Hγ22,Cγ2,Hγ23 a Hγ21,Cγ2,Hγ22 a Hγ21,Cγ2,Hγ23 δ a(cγh 3 ) Cγ2H 3 asym. def. 47 a Hγ21,Cγ2,Hγ22 a Hγ21,Cγ2,Hγ23 δ a(cγh 3 ) Cγ2H 3 asym. def. 48 2a Hγ21,Cγ2,Cβ a Hγ22,Cγ2,Cβ a Hγ23,Cγ2,Cβ ρ(cγh 3 ) Cγ2H 3 rocking 49 a Hγ22,Cγ2,Cβ a Hγ23,Cγ2,Cβ ρ(cγh 3 ) Cγ2H 3 rocking 50 a Hδ1,Cδ,Hδ2 +a Hδ1,Cδ,Hδ3 +a Hδ2,Cδ,Hδ3 δ s(cδh 3 ) CδH 3 sym. def. a Hδ1,Cδ,Cγ1 a Hδ2,Cδ,Cγ1 a Hδ3,Cδ,Cγ1 51 2a Hδ2,Cδ,Hδ3 a Hδ1,Cδ,Hδ2 a Hδ1,Cδ,Hδ3 δ a(cδh 3 ) CδH 3 asym. def. 52 a Hδ1,Cδ,Hδ2 a Hδ1,Cδ,Hδ3 δ a(cδh 3 ) CδH 3 asym. def. 53 2a Hδ1,Cδ,Cγ1 a Hδ2,Cδ,Cγ1 a Hδ3,Cδ,Cγ1 ρ(cδh 3 ) CδH 3 rocking 54 a Hδ2,Cδ,Cγ1 a Hδ3,Cδ,Cγ1 ρ(cδh 3 ) CδH 3 rocking 55 d x,n,cα,x τ(nh + 3 ) NH + 3 torsion 56 d x,cα,c,x τ(co 2 ) CO 2 torsion 57 d x,cα,cβ,x τ(cαcβ) CαCβ torsion 58 d x,cβ,cγ1,x τ(cβcγ1) CβCγ1 torsion 59 d x,cβ,cγ2,x τ(cγ2h 3 ) Cγ2H 3 torsion 60 d x,cγ1,cδ,x τ(cδh 3 ) CδH 3 torsion a arbiary numbering b b: bond, a: angle, d: dihedral, i: improper dihedral. Normalization factors are omitted and correspond to ( P c 2 i )1/2 c ν: setching, δ: bending, ρ: rocking, t: twisting, ω: wagging, τ: torsion 11

Table S9: Calculated frequencies, infrared intensities, irreducible group representation, and potential energy disibutions for β glycine zwitterion. number freq. IR int. irrep. P.E.D. (greater than 10%) (cm 1 ) ((D/Å) 2 /u) 24 697 0.0 A 40δ(CO 2 ),18ω(CO 2 ),16δ(NCαC) 23 696 1.7 B 38δ(CO 2 ),18ω(CO 2 ),16δ(NCαC) 22 626 0.0 A 80τ(NH + 3 ) 21 618 0.5 B 80τ(NH + 3 ),12ω(CO 2 ) 20 569 0.1 A 30ω(CO 2 ),18δ(CO 2 ),14ν(CαC),14ρ(CαH 2 ),12τ(NH + 3 ) 19 566 1.7 B 28ω(CO 2 ),18δ(CO 2 ),14ν(CαC),14ρ(CαH 2 ),14τ(NH + 3 ) 18 477 0.1 A 44ρ(CO 2 ),18δ(NCαC) 17 473 3.0 B 42ρ(CO 2 ),18δ(NCαC) 16 356 0.1 A 56δ(NCαC),34ρ(CO 2 ) 15 354 8.1 B 58δ(NCαC),34ρ(CO 2 ) 14 249 5.8 B 72rot,20τ(CO 2 ) 13 240 1.2 A 78rot,16τ(CO 2 ) 12 205 1.4 B 70rot,18 11 191 2.4 A 82rot 10 159 1.0 A 74τ(CO 2 ),16rot 9 154 0.0 B 50rot,30 8 129 0.0 B 42,40rot 7 120 0.3 A 46rot,34 6 103 0.0 A 86 5 99 0.0 B 50,34τ(CO 2 ) 4 66 0.1 A 70,20rot 3 0 0.0 B 90 2-0 0.0 A 84 1-0 0.0 B 50,30rot,22τ(CO 2 ) 12

Table S10: Calculated frequencies, infrared intensities, irreducible group representation, and potential energy disibutions for α glycine zwitterion. number freq. IR int. irrep. P.E.D. (greater than 10%) (cm 1 ) ((D/Å) 2 /u) 48 712 0.0 Ag 36δ(CO 2 ),24ω(CO 2 ),16δ(NCαC) 47 712 0.0 Bg 36δ(CO 2 ),24ω(CO 2 ),16δ(NCαC) 46 712 3.3 Bu 36δ(CO 2 ),20ω(CO 2 ),20δ(NCαC) 45 712 0.1 Au 36δ(CO 2 ),20ω(CO 2 ),16δ(NCαC) 44 660 0.1 Au 88τ(NH + 3 ) 43 659 0.0 Bu 88τ(NH + 3 ) 42 626 0.0 Bg 80τ(NH + 3 ) 41 624 0.0 Ag 84τ(NH + 3 ) 40 588 0.0 Ag 28ω(CO 2 ),24δ(CO 2 ),16ν(CαC) 39 588 0.0 Bg 28ω(CO 2 ),20δ(CO 2 ),16ν(CαC) 38 587 3.9 Bu 32ω(CO 2 ),24δ(CO 2 ),20ν(CαC),12ρ(CαH 2 ) 37 585 0.9 Au 36ω(CO 2 ),24δ(CO 2 ),20ν(CαC),12ρ(CαH 2 ) 36 469 6.0 Bu 40ρ(CO 2 ),16δ(NCαC) 35 468 0.0 Au 40ρ(CO 2 ),20δ(NCαC) 34 462 0.0 Ag 48ρ(CO 2 ),12δ(NCαC) 33 459 0.0 Bg 48ρ(CO 2 ),16δ(NCαC) 32 361 0.0 Bg 64δ(NCαC),28ρ(CO 2 ) 31 361 0.0 Ag 64δ(NCαC),28ρ(CO 2 ) 30 356 14.6 Bu 60δ(NCαC),36ρ(CO 2 ) 29 356 0.1 Au 60δ(NCαC),36ρ(CO 2 ) 28 254 1.5 Bu 92rot 27 225 0.9 Au 72rot,16τ(CO 2 ) 26 223 9.1 Bu 76rot,16τ(CO 2 ) 25 215 0.0 Ag 68rot 24 214 0.0 Bg 84rot 23 207 6.0 Au 92rot 22 182 0.0 Bg 72rot 21 180 0.0 Ag 56rot,28τ(CO 2 ) 20 174 0.0 Bg 40τ(CO 2 ),20,20rot 19 168 1.1 Bu 56τ(CO 2 ),32rot 18 167 0.0 Ag 36,32rot,16τ(CO 2 ) 17 163 1.1 Au 60τ(CO 2 ),12rot 16 159 0.0 Ag 40rot,20,12τ(CO 2 ) 15 157 0.0 Bg 52rot,28 14 134 1.1 Au 64rot,24τ(CO 2 ) 13 133 0.2 Bu 64rot,28τ(CO 2 ) 12 114 0.0 Bg 64,24τ(CO 2 ) 11 110 0.0 Ag 52,24τ(CO 2 ),24rot 10 102 0.0 Bg 76,16τ(CO 2 ) 9 98 0.0 Ag 80 8 98 0.1 Bu 100 7 96 0.1 Au 100 6 67 0.0 Au 92 5 61 0.0 Bg 76,12rot 4 55 0.0 Ag 72,16rot 3-0 0.0 Au 84 2-0 0.0 Bu 100 1-0 0.0 Bu 100 13

Table S11: Calculated frequencies, infrared intensities, irreducible group representation, and potential energy disibutions for glycine cation. number freq. IR int. irrep. P.E.D. (greater than 10%) (cm 1 ) ((D/Å) 2 /u) 60 638 0.5 Au 48δ(CO 2 H),24δ(NCαC) 59 637 0.0 Ag 48δ(CO 2 H),24δ(NCαC) 58 633 0.9 Bu 48δ(CO 2 H),20δ(NCαC) 57 632 0.0 Bg 48δ(CO 2 H),20δ(NCαC) 56 570 0.0 Bg 64ω(CO 2 H),24ρ(CαH 2 ) 55 568 0.1 Bu 64ω(CO 2 H),24ρ(CαH 2 ) 54 566 0.0 Ag 68ω(CO 2 H),28ρ(CαH 2 ) 53 564 0.1 Au 68ω(CO 2 H),28ρ(CαH 2 ) 52 496 0.0 Ag 40ρ(CO 2 H),20δ(CO 2 H) 51 496 0.0 Au 40ρ(CO 2 H),24δ(CO 2 H) 50 491 0.0 Bg 40ρ(CO 2 H),20δ(CO 2 H),12δ(NCαC) 49 490 1.2 Bu 40ρ(CO 2 H),20δ(CO 2 H),12δ(NCαC) 48 461 0.0 Ag 56τ(NH + 3 ),40ν a(cl HN) 47 461 0.5 Au 56τ(NH + 3 ),40ν a(cl HN) 46 459 0.0 Bg 92ν a(cl HN) 45 458 0.8 Bu 92ν a(cl HN) 44 313 0.0 Bg 60δ(NCαC),36ρ(CO 2 H) 43 308 8.6 Bu 60δ(NCαC),36ρ(CO 2 H) 42 294 0.0 Ag 52δ(NCαC),32ρ(CO 2 H) 41 293 8.9 Au 52δ(NCαC),32ρ(CO 2 H) 40 235 0.0 Bg 40ν s(cl HN),32τ(CO 2 H),16rot 39 223 2.7 Bu 40ν s(cl HN),36τ(CO 2 H) 38 206 0.0 Ag 68ν s(cl HN),44ν a(cl HN) 37 206 1.2 Au 52ν s(cl HN),44ν a(cl HN),16rot 36 202 0.0 Bg 44ν s(cl HN),40rot,32τ(NH + 3 ) 35 199 0.7 Bu 44ν s(cl HN),40τ(NH + 3 ),36rot 34 197 0.0 Ag 32τ(CO 2 H),24rot 33 195 6.1 Au 28ν s(cl HN),28τ(CO 2 H),20rot 32 195 0.0 Bg 52rot,32ν(Cl HO) 31 194 9.8 Bu 52rot,36ν(Cl HO) 30 182 0.0 Ag 36ν(Cl HO),28τ(CO 2 H),24rot,12 29 181 0.2 Au 36ν(Cl HO),24rot,24τ(CO 2 H),12 28 159 0.0 Au 76rot 27 158 0.0 Ag 72rot,20ν a(cl HN) 26 156 0.0 Bg 60τ(CO 2 H),12rot 25 152 0.0 Ag 32τ(NH + 3 ),24τ(CO 2 H),16rot 24 152 1.0 Bu 52τ(CO 2 H),36τ(NH + 3 ) 23 152 1.4 Au 48τ(NH + 3 ),20ν a(cl HN),20τ(CO 2 H) 22 147 0.0 Bg 36τ(NH + 3 ),28rot,20ν a(cl HN) 21 139 1.1 Bu 28rot,20ν a(cl HN),12τ(CO 2 H) 20 124 0.0 Ag 52,20τ(NH + 3 ),16rot 19 123 0.0 Bg 52ν(Cl HO),24τ(NH + 3 ) 18 118 0.1 Au 44ν(Cl HO),20τ(CO 2 H),16rot 17 117 0.0 Ag 48ν(Cl HO),16τ(CO 2 H) 16 116 0.5 Bu 48ν(Cl HO),20rot 15 110 0.0 Bg 48rot,20 14 109 0.0 Au 88rot 13 100 0.0 Ag 48rot,24 12 100 0.1 Au 68,12τ(NH + 3 ) 11 90 2.3 Bu 72rot 10 90 0.0 Bg 44,36rot 9 86 0.0 Bu 84 8 81 0.0 Ag 80 7 81 0.0 Bg 100 6 77 0.0 Au 92 5 61 0.0 Bg 100 4 60 0.0 Ag 88 3-0 0.0 Au 84 2-0 0.0 Bu 92 1-0 0.0 Bu 88 14

Table S12: Calculated frequencies, infrared intensities, irreducible group representation, and potential energy disibutions for glycine anion. number freq. IR int. irrep. P.E.D. (greater than 10%) (cm 1 ) ((D/Å) 2 /u) 60 674 0.0 B2 40δ(CO 2 ),16ν(CαC),16δ(NCαC),12ρ(CO 2 ) 59 673 4.0 B1 32δ(CO 2 ),16ν(CαC),16ρ(CO 2 ),12δ(NCαC) 58 672 0.1 B3 44δ(CO 2 ),20δ(NCαC),16ν(CαC),12ρ(CO 2 ) 57 672 0.0 A 36δ(CO 2 ),16ρ(CO 2 ),16ν(CαC),16δ(NCαC) 56 571 0.0 B1 56ω(CO 2 ),24ρ(CαH 2 ) 55 570 0.0 A 52ω(CO 2 ),24ρ(CαH 2 ) 54 569 0.1 B2 44ω(CO 2 ),20ρ(CαH 2 ) 53 568 1.2 B3 48ω(CO 2 ),20ρ(CαH 2 ) 52 538 0.3 B1 52ν(ONa + ),12ρ(CO 2 ) 51 536 0.0 A 44ν(ONa + ),16ρ(CO 2 ) 50 534 4.9 B2 52ν(ONa + ),12ρ(CO 2 ) 49 531 0.3 B3 56ν(ONa + ),12ρ(CO 2 ) 48 510 0.2 B2 40rot,28,24δ(CONa + ) 47 507 0.0 B3 36rot,28,24δ(CONa + ) 46 497 0.0 A 40rot,24δ(CONa + ),12 45 496 5.1 B1 40rot,16δ(CONa + ),12 44 488 2.3 B2 20rot,16ν(ONa + ) 43 486 0.0 B1 16ν(ONa + ),16δ(NCαC),12δ(CONa + ),12rot 42 485 0.0 B3 16δ(CONa + ),12ρ(CO 2 ),12ν(ONa + ) 41 481 0.0 A 24ν(ONa + ),16,12δ(CONa + ),12δ(NCαC) 40 453 3.3 B3 44rot,16ν(ONa + ),16τ(CONa + ) 39 450 0.0 A 52rot,20τ(CONa + ),16 38 448 0.1 B1 24τ(CONa + ),24rot,20 37 445 0.1 B2 20τ(CONa + ),20rot,16ρ(CO 2 ),12 36 409 0.6 B3 92τ(NH 2 ) 35 404 3.2 B1 92τ(NH 2 ) 34 399 0.0 A 96τ(NH 2 ) 33 393 1.3 B2 92τ(NH 2 ) 32 312 1.4 B2 56δ(NCαC),24ρ(CO 2 ) 31 305 0.0 A 52δ(NCαC),28ρ(CO 2 ),12δ(CONa + ) 30 301 0.5 B1 52δ(NCαC),28ρ(CO 2 ) 29 301 0.6 B3 60δ(NCαC),28ρ(CO 2 ) 28 219 0.0 B3 44δ(CONa + ),16 27 216 0.8 B1 28rot,24,16τ(CO 2 ) 26 216 0.1 B2 32τ(CO 2 ),28rot,16τ(CONa + ) 25 213 0.1 B2 28δ(CONa + ),20,20rot 24 211 0.0 B3 40τ(CO 2 ),40rot 23 209 0.0 A 32,16rot,12δ(CONa + ) 22 205 0.0 A 36τ(CO 2 ),28rot 21 204 0.2 B1 36τ(CONa + ),16τ(CO 2 ),12rot 20 201 0.1 B1 28δ(CONa + ),20τ(CO 2 ),12rot 19 193 1.5 B3 52τ(CONa + ) 18 189 0.0 A 44τ(CONa + ),16τ(CO 2 ) 17 185 1.3 B2 36τ(CONa + ),16δ(CONa + ),16rot 16 152 0.1 B2 64 15 144 0.0 A 32rot,28 14 140 0.3 B1 40rot,36 13 138 0.0 A 68,16τ(CONa + ) 12 135 0.2 B3 32,20rot,16τ(CO 2 ) 11 124 0.2 B1 48,20τ(CONa + ) 10 102 0.2 B2 52τ(CO 2 ),32rot,16 9 99 0.0 B1 48τ(CO 2 ),28rot,20 8 98 0.0 A 44τ(CO 2 ),28rot,20 7 93 0.5 B3 36rot,24,24τ(CO 2 ) 6 77 0.0 B2 36rot,28 5 74 0.1 B3 44rot,40,12τ(CO 2 ) 4 66 0.0 A 44,36rot 3 0 0.0 B3 56,20rot 2-0 0.0 B2 80 1-0 0.0 B1 44,32rot 15

Table S13: Calculated frequencies, infrared intensities, irreducible group representation, and potential energy disibutions for L-alanine zwitterion. number freq. IR int. irrep. P.E.D. (greater than 10%) (cm 1 ) ((D/Å) 2 /u) 60 752 0.3 B1 68ω(CO 2 ) 59 752 0.0 A 64ω(CO 2 ) 58 750 0.0 B3 64ω(CO 2 ) 57 748 1.3 B2 64ω(CO 2 ) 56 651 0.0 A 28δ(CO 2 ),24δ(NCαC),12ν(CαC) 55 648 0.9 B1 28δ(CO 2 ),24δ(NCαC),12ν(CαC) 54 647 0.2 B3 28δ(CO 2 ),24δ(NCαC) 53 644 0.4 B2 28δ(CO 2 ),24δ(NCαC),12ρ(CO 2 ) 52 575 1.5 B2 76τ(NH + 3 ) 51 574 0.3 B1 84τ(NH + 3 ) 50 570 0.3 B3 76τ(NH + 3 ) 49 568 0.0 A 80τ(NH + 3 ) 48 526 0.0 B2 28ρ(CO 2 ),16ν(CαC) 47 523 6.4 B3 28ρ(CO 2 ),12ν(CαC) 46 521 0.3 B1 28ρ(CO 2 ),16ν(CαC),16δ(CO 2 ) 45 517 0.0 A 24ρ(CO 2 ),16ν(CαC),16δ(CO 2 ) 44 422 5.6 B3 72δ(NCαCβ) 43 415 2.7 B2 76δ(NCαCβ) 42 408 0.8 B1 72δ(NCαCβ) 41 406 0.0 A 72δ(NCαCβ) 40 324 1.0 B1 36δ(NCαC),28ρ(CO 2 ) 39 319 0.8 B2 28ρ(CO 2 ),28δ(NCαC),16τ(CβH 3 ),16δ(CCαCβ) 38 306 0.0 A 28ρ(CO 2 ),28δ(NCαC),20τ(CβH 3 ) 37 304 4.1 B3 28ρ(CO 2 ),24δ(NCαC),24τ(CβH 3 ),16δ(CCαCβ) 36 277 1.3 B1 64δ(CCαCβ),12ω(CO 2 ) 35 268 0.0 A 52δ(CCαCβ),16δ(NCαC),12ρ(CO 2 ) 34 267 2.5 B2 60δ(CCαCβ),12ω(CO 2 ),12δ(NCαC) 33 263 0.0 B3 40δ(CCαCβ),32τ(CβH 3 ) 32 256 0.0 A 76τ(CβH 3 ) 31 254 0.6 B3 32τ(CβH 3 ),24δ(NCαC),20ρ(CO 2 ),12δ(CCαCβ) 30 246 2.8 B2 64τ(CβH 3 ) 29 244 0.2 B1 60τ(CβH 3 ) 28 240 0.0 B3 72rot 27 232 0.1 B1 32τ(CO 2 ),32rot,24τ(CβH 3 ) 26 226 7.4 B2 44rot,20τ(CO 2 ),20τ(CβH 3 ) 25 222 0.0 A 48rot,36 24 206 0.2 B3 40,28rot,16τ(CO 2 ) 23 190 4.0 B1 72rot 22 184 0.0 A 64rot,28τ(CO 2 ) 21 182 0.2 B2 72rot,20τ(CO 2 ) 20 176 0.1 B2 60rot,36τ(CO 2 ) 19 160 0.1 B3 48rot,20τ(CO 2 ) 18 154 0.0 A 48rot,40τ(CO 2 ) 17 151 0.6 B1 60rot,32 16 149 0.0 B3 60,12rot 15 147 0.1 B2 88 14 143 0.4 B1 32,28τ(CO 2 ),20rot 13 143 0.0 A 40,40rot 12 140 0.0 B3 44τ(CO 2 ),24rot,20 11 114 0.4 B2 52rot,28,12τ(CO 2 ) 10 113 0.0 A 68 9 112 0.1 B1 76 8 107 0.0 A 40rot,36 7 96 0.0 B3 56,24rot 6 92 0.1 B2 88 5 89 0.0 B1 52rot,28 4 83 0.0 A 92 3 0 0.0 B1 88 2 0 0.0 B3 64,20rot 1 0 0.0 B2 80 16

Table S14: Calculated frequencies, infrared intensities, irreducible group representation, and potential energy disibutions for L-valine zwitterion. number freq. IR int. irrep. P.E.D. (greater than 10%) (cm 1 ) ((D/Å) 2 /u) 80 759 0.2 A 32δ(CO 2 ),16ω(CO2 ),16ν(CαCβ) 79 759 1.0 B 34δ(CO 2 ),16ω(CO2 ),16ν(CαCβ) 78 734 0.3 B 48ω(CO 2 ),18ν(CαCβ) 77 734 0.1 A 48ω(CO 2 ),18ν(CαCβ) 76 714 2.4 B 46δ(CO 2 ),16δ(NCαC) 75 713 0.0 A 44δ(CO 2 ),16δ(NCαC) 74 656 0.5 B 18δ(NCαC),16δ(CO 2 ),16ω(CO2 ),12ρ(CO2 ) 73 654 0.3 A 18δ(NCαC),16δ(CO 2 ),16ω(CO2 ),14ρ(CO2 ) 72 564 0.1 B + 86τ(NH 3 ) 71 564 0.3 A + 88τ(NH 3 ) 70 552 0.3 A + 80τ(NH 3 ) 69 551 0.2 B + 74τ(NH 3 ) 68 540 2.8 B 16ρ(CO 2 ),12ν(NCα),12δ(NCαCβ) 67 537 0.6 A 24ρ(CO 2 ),14ν(NCα),12δ(NCαCβ) 66 533 1.7 A 16ρ(CO 2 ),16ν(CαC),16ν(NCα),12δ(CO2 ) 65 531 1.1 B 18ρ(CO 2 ),14ν(CαC) 64 462 0.1 A 36δ(CαCβCγ),14ν(CαC),14δ(CγCβCγ) 63 462 0.6 B 36δ(CαCβCγ),14ν(CαC),14δ(CγCβCγ) 62 444 0.6 B 28δ(NCαCβ),16ρ(CO 2 ),12δ(CγCβCγ) 61 442 0.5 A 28δ(NCαCβ),20ρ(CO 2 ),16δ(CγCβCγ) 60 427 1.4 B 26δ(NCαCβ),18δ(CαCβCγ),12ρ(CO 2 ) 59 426 1.0 A 26δ(NCαCβ),16δ(CαCβCγ),12ρ(CO 2 ),12δ(CγCβCγ) 58 402 2.3 B 42δ(CγCβCγ),14δ(NCαCβ) 57 398 0.2 A 40δ(CγCβCγ),16δ(NCαCβ),12ν(CαC) 56 371 2.3 B 50δ(CαCβCγ),16δ(CγCβCγ) 55 369 0.3 A 54δ(CαCβCγ),14δ(CγCβCγ) 54 358 1.0 B 44δ(CγCβCγ),14δ(NCαC) 53 353 0.1 A 50δ(CγCβCγ),22δ(CαCβCγ) 52 350 1.3 B 38ρ(CO 2 ),24δ(NCαC),18δ(CαCβCγ) 51 348 0.4 A 42δ(NCαC),38ρ(CO 2 ) 50 338 1.6 B 50δ(CαCβCγ) 49 332 0.6 A 46δ(CαCβCγ),12δ(NCαC) 48 300 0.1 A 28δ(NCαC),26ρ(CO 2 ) 47 300 1.8 B 24ρ(CO 2 ),24δ(NCαC) 46 284 2.5 B 24δ(CCαCβ),20τ(CO 2 ) 45 282 0.2 A 24δ(CCαCβ),16τ(CO 2 ),12rot 44 278 0.2 A 62τ(CγH 3 ) 43 278 0.3 B 60τ(CγH 3 ) 42 264 0.1 B 32δ(CαCβCγ),14δ(CCαCβ),14δ(NCαCβ) 41 262 0.9 B 26τ(CO 2 ),18τ(CγH3 ),12δ(CαCβCγ) 40 262 0.1 A 22δ(CαCβCγ),22δ(CCαCβ) 39 260 0.4 A 26τ(CγH 3 ),22δ(CαCβCγ),22δ(NCαCβ),14τ(CO 2 ) 38 242 0.2 B 54τ(CγH 3 ) 37 238 0.1 A 72τ(CγH 3 ) 36 233 0.1 B 18τ(CγH 3 ),16rot,12τ(CαCβ) 35 230 0.0 A 28τ(CO 2 ),20τ(CγH3 ),14δ(CCαCβ) 34 230 0.2 B 82τ(CγH 3 ) 33 228 0.0 A 62τ(CγH 3 ) 32 225 0.7 B 40τ(CO 2 ),16rot,14δ(CCαCβ) 31 220 2.8 A 28τ(CαCβ),26rot,22τ(CγH 3 ) 30 213 0.1 B 38τ(CγH 3 ),12τ(CαCβ) 29 206 0.1 A 22τ(CO 2 ),12τ(CγH3 ),12δ(CCαCβ) 28 205 0.8 B 36τ(CO 2 ),18δ(CCαCβ) 27 204 0.7 A 58τ(CγH 3 ),18rot 26 202 1.1 B 40τ(CγH 3 ),22rot,12τ(CO 2 ) 25 194 0.9 A 24τ(CO 2 ),20rot,12τ(CαCβ) 24 189 1.5 B 44rot,40τ(CαCβ) 23 182 1.8 A 24rot,24τ(CαCβ),18 22 159 0.2 B 30rot,28τ(CαCβ),14 21 157 0.1 A 38rot,34τ(CαCβ) 20 152 0.0 A 46,30rot 19 151 0.1 B 34rot,32,14τ(CαCβ) 18 146 0.1 A 48rot 17 144 0.2 B 38rot,28 16 138 0.0 A 32,30rot 15 137 0.2 B 36,30rot 14 128 0.0 A 68,14rot 13 123 0.0 B 44rot,22 12 114 0.0 A 40,26rot,16τ(CαCβ) 11 111 0.0 B 40τ(CαCβ),24rot,12 10 110 0.3 A 34rot,18,16τ(CαCβ) 9 106 0.1 B 50,26rot 8 99 0.5 A 38,28rot 7 92 0.1 B 62,12rot 6 85 0.0 A 46,24rot 5 83 0.1 B 62,14rot 4 81 0.0 B 54,18rot 3 77 0.0 A 62,18rot 2 56 0.0 A 44,36rot 1 56 0.0 B 44,38rot 17

Table S15: Calculated frequencies, infrared intensities, irreducible group representation, and potential energy disibutions for L-leucine zwitterion. number freq. IR int. irrep. P.E.D. (greater than 10%) (cm 1 ) ((D/Å) 2 /u) 88 752 0.0 B 66ω(CO 2 ) 87 752 0.1 A 62ω(CO 2 ) 86 747 0.0 A 66ω(CO 2 ) 85 746 1.0 B 64ω(CO 2 ) 84 666 0.4 B 26δ(CO 2 ),18δ(NCαC),14ρ(CO2 ) 83 665 0.1 A 24δ(CO 2 ),16δ(NCαC),12ρ(CO2 ) 82 659 1.7 B 26δ(CO 2 ),20δ(NCαC),12ρ(CO2 ) 81 655 0.0 A 24δ(CO 2 ),18δ(NCαC),12ρ(CO2 ) 80 579 0.1 A + 94τ(NH 3 ) 79 577 0.1 B + 86τ(NH 3 ) 78 573 0.6 A + 88τ(NH 3 ) 77 572 0.1 B + 86τ(NH 3 ) 76 525 0.1 A 18ρ(CO 2 ),12δ(NCαCβ) 75 525 2.3 B 14ρ(CO 2 ),14δ(NCαCβ) 74 519 0.1 B 16ρ(CO 2 ),12ν(CαC) 73 517 2.5 A 20ρ(CO 2 ) 72 440 0.4 A 34δ(CδCγCδ),12δ(CβCγCδ) 71 440 0.3 B 34δ(CδCγCδ),12δ(CβCγCδ) 70 438 0.0 B 30δ(CδCγCδ),16δ(CβCγCδ) 69 437 0.0 A 32δ(CδCγCδ),18δ(CβCγCδ) 68 430 0.4 B 30δ(CβCγCδ),16δ(NCαCβ) 67 428 2.2 A 36δ(CβCγCδ),12δ(NCαCβ) 66 428 0.6 B 34δ(CβCγCδ) 65 426 0.1 A 38δ(CβCγCδ) 64 390 2.6 A 24δ(CβCγCδ),24δ(NCαCβ),22δ(CδCγCδ) 63 390 1.2 B 28δ(CβCγCδ),20δ(NCαCβ),16δ(CδCγCδ) 62 385 0.2 B 24δ(CβCγCδ),20δ(CδCγCδ),18δ(NCαCβ) 61 382 0.0 A 26δ(CβCγCδ),24δ(CδCγCδ),22δ(NCαCβ) 60 352 5.1 B 20δ(CCαCβ),16δ(NCαC),12δ(CδCγCδ) 59 342 5.7 B 30ρ(CO 2 ),24δ(NCαC) 58 341 1.0 A 40δ(NCαC),30ρ(CO 2 ) 57 338 0.9 A 24δ(CδCγCδ),18δ(NCαCβ),16δ(CβCγCδ) 56 333 0.4 B 24δ(CδCγCδ),14δ(CβCγCδ),14δ(NCαCβ) 55 330 0.6 A 24δ(NCαCβ),18δ(CδCγCδ),18δ(CβCγCδ) 54 313 0.1 A 40δ(NCαC),34ρ(CO 2 ) 53 309 0.0 B 38δ(NCαC),36ρ(CO 2 ) 52 286 0.2 B 38δ(CCαCβ),16τ(CδH 3 ) 51 282 0.2 A 36τ(CδH 3 ),24δ(CCαCβ),12δ(CβCγCδ) 50 280 0.1 A 26δ(CCαCβ),22τ(CδH 3 ),12δ(CβCγCδ) 49 279 0.2 B 40τ(CδH 3 ),16δ(CCαCβ) 48 266 0.2 B 18δ(CαCβCγ),18rot,14δ(CβCγCδ) 47 258 5.1 A 28δ(CαCβCγ),24rot,18δ(CβCγCδ) 46 249 1.1 B 32τ(CδH 3 ),16δ(CαCβCγ),14rot 45 246 0.5 A 30τ(CδH 3 ),16rot,14δ(CCαCβ) 44 245 0.8 A 24δ(CCαCβ),22τ(CδH 3 ) 43 244 0.9 B 38τ(CδH 3 ),14δ(CαCβCγ) 42 242 0.9 A 48τ(CδH 3 ),12δ(CαCβCγ),12δ(CβCγCδ) 41 240 0.2 B 42τ(CδH 3 ),22δ(CCαCβ) 40 234 0.0 B 88τ(CδH 3 ) 39 231 0.0 A 78τ(CδH 3 ) 38 225 0.2 B 80τ(CδH 3 ) 37 224 0.4 A 80τ(CδH 3 ) 36 220 1.1 B 20rot,14τ(CO 2 ) 35 207 0.3 B 40τ(CO 2 ),20rot 34 199 0.0 A 58τ(CO 2 ) 33 190 0.2 A 22rot,18τ(CαCβ),16δ(CαCβCγ) 32 183 0.6 A 22τ(CO 2 ),22τ(CαCβ),16rot 31 181 0.1 A 52τ(CO 2 ) 30 181 0.6 B 30τ(CO 2 ),20τ(CαCβ),12δ(CαCβCγ) 29 174 0.1 B 24δ(CαCβCγ),18τ(CO 2 ),14τ(CαCβ) 28 166 0.0 B 42τ(CO 2 ),14rot,12τ(CαCβ) 27 157 0.6 A 26τ(CβCγ),18rot 26 154 0.3 B 58τ(CβCγ) 25 151 0.1 A 32τ(CβCγ),20,14τ(CαCβ) 24 144 0.1 B 44,28τ(CβCγ) 23 130 0.1 A 38τ(CβCγ),18rot,16 22 126 0.0 A 32,28rot,12τ(CβCγ) 21 124 0.0 B 32rot,12 20 114 0.1 B 38rot,28,18τ(CαCβ) 19 113 0.0 A 38rot,36 18 109 0.0 A 30τ(CαCβ),28,22rot 17 103 0.0 B 70rot 16 102 0.0 A 42rot,14τ(CβCγ),14,12τ(CαCβ) 15 101 0.0 B 32τ(CβCγ),28,18rot 14 98 0.0 A 34rot,14τ(CO 2 ),12 13 96 0.0 B 48,18rot 12 90 0.0 A 64 11 89 0.1 B 28rot,22,18τ(CαCβ),12τ(CβCγ) 10 86 0.0 A 38,38rot 9 81 0.0 B 48,38rot 8 75 0.1 A 52,26rot 7 69 0.0 A 28τ(CαCβ),24,20rot 6 67 0.0 B 30τ(CαCβ),22,16rot 5 64 0.0 A 58 4 64 0.0 B 80 3 49 0.0 B 60,16rot 2 43 0.0 A 52,20rot 1 40 0.0 B 44,18rot 18

Table S16: Calculated frequencies, infrared intensities, irreducible group representation, and potential energy disibutions for L-isoleucine zwitterion. number freq. IR int. irrep. P.E.D. (greater than 10%) (cm 1 ) ((D/Å) 2 /u) 88 751 0.0 A 32ρ(Cγ1H 2 ),14ρ(CδH 3 ) 87 751 0.7 B 32ρ(Cγ1H 2 ),14ρ(CδH 3 ) 86 731 0.4 B 38ω(CO 2 ),12ν(CαCβ) 85 731 0.2 A 38ω(CO 2 ),12ν(CαCβ) 84 704 2.0 B 48δ(CO 2 ) 83 702 0.0 A 48δ(CO 2 ) 82 662 0.7 B 24δ(CO 2 ),22δ(NCαC),12ω(CO2 ) 81 661 0.2 A 24δ(CO 2 ),22δ(NCαC),12ρ(CO2 ),12ω(CO2 ) 80 565 0.1 B + 78τ(NH 3 ) 79 565 0.2 A + 82τ(NH 3 ) 78 556 0.1 A + 60τ(NH 3 ) 77 553 0.1 B + 74τ(NH 3 ) 76 547 0.7 B 22ρ(CO 2 ),18δ(NCαCβ),14ν(NCα) 75 544 0.8 A + 28τ(NH 3 ),16ρ(CO2 ),14δ(NCαCβ) 74 525 2.5 B 18ρ(CO 2 ),18ν(CαC),14δ(CO2 ),12ν(NCα) 73 525 1.5 A 18ν(CαC),16ρ(CO 2 ),14δ(CO2 ),14ν(NCα) 72 474 0.3 A 28δ(CαCβCγ2),14ω(CO 2 ) 71 473 0.5 B 28δ(CαCβCγ2),14ω(CO 2 ) 70 438 0.5 B 28δ(CγCβCγ),12δ(NCαCβ) 69 436 0.0 A 32δ(CγCβCγ) 68 434 1.6 B 24δ(CγCβCγ),18δ(NCαCβ),12ρ(CO 2 ) 67 432 1.7 A 26δ(CγCβCγ),16δ(NCαCβ),12ρ(CO 2 ) 66 416 1.2 B 30δ(CαCβCγ2),16δ(CβCγ1Cδ),12ν(CαCβ) 65 414 0.0 A 34δ(CαCβCγ2),16δ(CβCγ1Cδ),12ν(CαCβ) 64 392 3.9 B 18δ(CγCβCγ),16δ(NCαC),16δ(NCαCβ),14ν(CαC) 63 388 1.0 A 20δ(CγCβCγ),18δ(NCαCβ),16ν(CαC),14δ(NCαC) 62 366 1.1 B 16δ(CβCγ1Cδ),14δ(CγCβCγ),14δ(NCαCβ) 61 360 0.3 A 18δ(CβCγ1Cδ),16δ(NCαCβ) 60 347 2.6 B 30ρ(CO 2 ),16δ(NCαC) 59 343 0.4 A 36ρ(CO 2 ),32δ(NCαC) 58 338 1.0 B 24δ(CαCβCγ2),18δ(CβCγ1Cδ) 57 337 0.2 A 28δ(CβCγ1Cδ),18δ(CαCβCγ2) 56 314 1.3 B 16δ(CγCβCγ),16δ(NCαC),12δ(NCαCβ) 55 310 0.0 A 16δ(NCαC),14ρ(CO 2 ),14δ(CγCβCγ),14δ(NCαCβ) 54 306 0.4 A 14τ(Cγ2H 3 ),14δ(CγCβCγ),12δ(CαCβCγ2) 53 303 0.2 B 20δ(NCαC),18ρ(CO 2 ),12τ(Cγ2H3 ) 52 291 0.6 B 20δ(CαCβCγ1),12δ(CβCγ1Cδ) 51 282 0.1 A 24δ(CαCβCγ1),18δ(CγCβCγ),12δ(CCαCβ) 50 271 0.2 A 44τ(Cγ2H 3 ),14τ(CδH 3 ) 49 271 0.6 B 32τ(Cγ2H 3 ),12δ(CCαCβ) 48 257 1.6 B 24δ(CCαCβ),14τ(Cγ2H 3 ) 47 248 0.0 A 24τ(CδH 3 ),20δ(CCαCβ),16δ(CαCβCγ2) 46 242 0.3 B 34τ(CδH 3 ),18δ(CαCβCγ2) 45 240 0.0 A 30δ(CCαCβ),14δ(CαCβCγ2) 44 236 0.9 B 26δ(CCαCβ) 43 234 0.1 A 16δ(CCαCβ),14τ(CαCβ) 42 228 0.1 A 48τ(CO 2 ) 41 227 1.0 B 42τ(CO 2 ),12δ(CαCβCγ1) 40 224 1.0 A 24τ(Cγ2H 3 ),20δ(CαCβCγ1),12τ(CδH 3 ),12δ(CβCγ1Cδ) 39 222 0.0 B 40τ(CδH 3 ),26τ(Cγ2H 3 ) 38 217 0.8 A 50τ(CδH 3 ) 37 215 0.5 B 16τ(CδH 3 ),16τ(CO 2 ),14δ(CαCβCγ1) 36 213 0.4 B 20τ(CδH 3 ),16τ(CO 2 ),16δ(CαCβCγ1) 35 210 0.7 A 22τ(CO 2 ),20τ(CδH3 ),16τ(Cγ2H 3 ) 34 201 0.1 B 44τ(Cγ2H 3 ),12τ(CδH 3 ),12τ(CO 2 ) 33 200 0.1 A 36τ(Cγ2H 3 ),26τ(CO 2 ) 32 193 0.2 B 40τ(CO 2 ) 31 183 0.5 A 26τ(CO 2 ),26rot,14τ(CαCβ) 30 177 0.4 B 32rot,18τ(CαCβ),12τ(CβCγ1) 29 172 0.8 A 32rot,16,14τ(CαCβ) 28 168 2.7 A 28τ(CβCγ1),28rot 27 168 1.4 B 36rot,24τ(CαCβ) 26 161 0.2 B 56τ(CβCγ1),16rot 25 158 0.4 A 32τ(CβCγ1),16 24 139 0.1 A 50τ(CβCγ1),12rot 23 138 0.1 B 36τ(CβCγ1),20rot,18 22 130 0.0 A 42rot,20 21 128 0.1 B 44rot,30τ(CαCβ) 20 124 0.0 A 40τ(CαCβ) 19 122 0.0 B 52,16rot 18 121 0.0 A 52rot 17 119 0.0 B 30rot,22,20τ(CαCβ) 16 116 0.0 A 44,16rot 15 114 0.2 B 42rot,28τ(CβCγ1) 14 110 0.0 A 28,20rot,18τ(CαCβ) 13 105 0.1 B 40rot,22,22τ(CαCβ) 12 101 0.1 B 40rot,28 11 98 0.2 A 60 10 96 0.0 A 36rot,22 9 96 0.1 B 62 8 95 0.0 A 34,34rot 7 83 0.3 B 52,20rot 6 74 0.0 A 36,32rot 5 73 0.1 B 56,28rot 4 67 0.0 A 62,30rot 3 31 0.0 B 64,26rot 2 27 0.0 A 70,20rot 1-0 0.0 B 58,20rot 19

Table S17: Far infrared experimental frequencies and intensities, assignments, and groups of calculated mode frequencies and symmey, for β glycine zwitterion. exp. calc. freq. b nb. a freq. b int. c assign. d A B 12 - - δ(co 2 ) 697 696 11 521 m τ(nh + 3 ) 626 618 10 608 m ω(co 2 ) 569 566 9 483 m ρ(co 2 ) 477 473 8 377 m,b δ(ncαc) 356 354 7 207 vs rot 240 249 6 181 s rot 191 205 5 - - rot 120 154 4 153 s τ(co 2 ) 159 99 3 61 w 66 0 2 - - -0 129 1 - - 103-0 a Index based on lowest frequency of calculated mode groups b Wavenumber (cm 1 ) c Qualitative intensity: very song (vs), song (s), medium (m), weak (w), very weak (vw), shoulder (sh), broad (b) d Mode definitions: ν (setching), δ (bending), ρ (rocking), t (twisting), ω (wagging), and τ (torsion). 20

Table S18: Far infrared experimental frequencies and intensities, assignments, and groups of calculated mode frequencies and symmey, for α glycine zwitterion. exp. calc. freq. nb. freq. int. assign. Ag Bg Au Bu 12 - - δ(co 2 ) 712 712 712 712 11 523 sh τ(nh + 3 ) 624 626 660 659 10 606 m ω(co 2 ) 588 588 585 587 9 500 m ρ(co 2 ) 462 459 468 469 8 352 m δ(ncαc) 361 361 356 356 7 227 sh rot 215 214 225 223 6 194 sh rot 180 182 207 254 5 165 s τ(co 2 ) 167 174 163 168 4 134 s rot 159 157 134 133 3 - - 110 114 96 98 2 - - 55 61-0 -0 1 62 w 98 102 67-0 21

Table S19: Far infrared experimental frequencies and intensities, assignments, and groups of calculated mode frequencies and symmey, for glycine cation. exp. calc. freq. nb. freq. int. assign. Ag Bg Au Bu 15 638 w δ(co 2 H) 637 632 638 633 14 - - ω(co 2 H) 566 570 564 568 13 497 m ρ(co 2 H) 496 491 496 490 12 - - τ(nh + 3 )/ν a(cl HN) 461 459 461 458 11 296 m δ(ncαc) 294 313 293 308 10 - - ν s(cl HN) 206 202 206 199 9 - - ν s(cl HN)/τ(CO 2 ) 197 235 195 223 8 166 s rot/ν(cl HO) 182 195 181 194 7 148 s τ(co 2 H)/τ(NH + 3 ) 152 156 152 152 6 - - rot/ν a(cl HN) 158 147 159 139 5 - - ν(cl HO)/τ(CO 2 H)/rot 117 123 118 116 4 89 m rot 100 110 109 90 3 - - 60 90-0 86 2 - - 81 61 77-0 1 - - 124 81 100-0 22

Table S20: Far infrared experimental frequencies and intensities, assignments, and groups of calculated mode frequencies and symmey, for glycine anion. exp. calc. freq. nb. freq. int. assign. A B1 B2 B3 15 677 m δ(co 2 ) 672 673 674 672 14 580 w ω(co 2 ) 570 571 569 568 13 513 m ν(ona + ) 536 538 534 531 12 446 w,b rot/δ(cona + ) 497 496 510 507 11 - - ν(cona + )/δ(cona + ) 481 486 488 485 10 376 w rot/τ(cona + ) 450 448 445 453 9 256 m τ(nh 2 ) 399 404 393 409 8 311 m δ(ncαc)/ρ(co 2 ) 305 301 312 301 7 211 vs /δ(cona + ) 209 216 213 219 6 - - τ(co 2 )/rot 205 204 216 211 5 163 s τ(cona + ) 189 201 185 193 4 114 m τ(co 2 )/rot 98 99 102 93 3 - - 138 124 152 0 2 131 m /rot 144 140-0 135 1 - - /rot 66-0 77 74 23

Table S21: Far infrared experimental frequencies and intensities, assignments, and groups of calculated mode frequencies and symmey, for L-alanine zwitterion. exp. calc. freq. nb. freq. int. assign. A B1 B2 B3 15 - - ω(co 2 ) 752 752 748 750 14 648 m δ(co 2 )/δ(ncαc) 651 648 644 647 13 486 w τ(nh + 3 ) 568 574 575 570 12 539 s ρ(co 2 ) 517 521 526 523 11 409 s δ(ncαcβ) 406 408 415 422 10 324 m δ(ncαc)/ρ(co 2 ) 306 324 319 304 9 278 m δ(ccαcβ) 268 277 267 263 8 259 w τ(cβh 3 ) 256 244 246 254 7 221 sh rot 184 190 182 160 6 173 m τ(co 2 ) 154 143 176 206 5 201 m rot 143 232 226 240 4 - - rot 222 151 114 140 3 109 w 113 0 147 149 2 79 w 83 112 92 0 1 - - 107 89 0 96 24

Table S22: Far infrared experimental frequencies and intensities, assignments, and groups of calculated mode frequencies and symmey, for L-valine zwitterion. exp. calc. freq. nb. freq. int. assign. A B 40 - - δ(co 2 ) 759 759 39 - - ω(co 2 ) 734 734 38 - - δ(co 2 ) 713 714 37 663 m δ(ncαc)/δ(co 2 )/ 654 656 ω(co 2 ) 36 495 w τ(nh + 3 ) 564 564 35 495 w τ(nh + 3 ) 552 551 34 540 s ρ(co 2 ) 537 540 33 540 s ρ(co 2 ) 533 531 32 472 w δ(cαcβcγ) 462 462 31 440 sh δ(ncαcβ) 442 444 30 427 m δ(ncαcβ) 426 427 29 399 m δ(cγcβcγ) 398 402 28 374 s δ(cαcβcγ) 369 371 27 - - δ(cγcβcγ) 353 358 26 - - δ(ncαc)/ρ(co 2 ) 348 350 25 333 s δ(cαcβcγ) 332 338 24 292 m δ(ncαc)/ρ(co 2 ) 300 300 23 279 m δ(ccαcβ) 282 284 22 - - τ(cγh 3 ) 278 278 21 - - δ(cαcβcγ)/δ(ccαcβ) 262 264 20 - - τ(cγh 3 )/δ(cαcβcγ)/ 260 262 τ(co 2 ) 19 - - τ(cγh 3 ) 238 242 18 - - τ(cγh 3 ) 228 230 17 228 m τ(co 2 ) 230 225 16 218 sh τ(cαcβ)/τ(cγh 3 ) 220 213 15 - - τ(co 2 ) 206 205 14 180 s τ(cγh 3 )/rot 204 202 13 - - rot 194 233 12 145 s τ(cαcβ) 182 189 11 - - rot/τ(cαcβ) 157 159 10 - - 152 151 9 121 sh rot 146 144 8 - - 128 137 7 - - rot 114 123 6 - - τ(cαcβ)/rot 110 111 5 - - 138 106 4 96 m 99 92 3 76 vw 85 83 2 - - 77 81 1 56 w /rot 56 56 25

Table S23: Far infrared experimental frequencies and intensities, assignments, and groups of calculated mode frequencies and symmey, for L-leucine zwitterion. exp. calc. freq. nb. freq. int. assign. A B 44 - - ω(co 2 ) 752 752 43 - - ω(co 2 ) 747 746 42 668 m δ(co 2 ) 665 666 41 668 m δ(co 2 ) 655 659 40 504 vw τ(nh + 3 ) 579 577 39 504 vw τ(nh + 3 ) 573 572 38 534 s ρ(co 2 ) 525 525 37 534 s ρ(co 2 ) 517 519 36 456 sh δ(cδcγcδ) 440 440 35 456 sh δ(cδcγcδ) 437 438 34 442 m δ(cβcγcδ) 428 430 33 442 m δ(cβcγcδ) 426 428 32 402 s δ(cβcγcδ) 390 390 31 402 s δ(cβcγcδ) 382 385 30 364 m δ(ncαc)/ρ(co 2 ) 341 352 29 343 s δ(cδcγcδ)/ρ(co 2 )/ 338 342 δ(ncαcβ) 28 330 s δ(cδcγcδ)/δ(ncαcβ)/ 330 333 δ(cβcγcδ) 27 - - δ(ncαc)/ρ(co 2 ) 313 309 26 - - δ(ccαcβ)/τ(cδh 3 ) 280 286 25 - - τ(cδh 3 )/δ(ccαcβ) 282 279 24 223 m δ(cαcβcγ)/rot 258 266 23 203 s τ(cδh 3 ) 246 249 22 - - τ(cδh 3 )/δ(cαcβcγ) 242 244 21 - - τ(cδh 3 )/δ(ccαcβ) 245 240 20 - - τ(cδh 3 ) 231 234 19 - - τ(cδh 3 ) 224 225 18 170 m τ(co 2 ) 199 220 17 - - τ(co 2 ) 181 207 16 138 sh τ(co 2 )/τ(cαcβ) 183 181 15 - - δ(cαcβcγ)/τ(cαcβ) 190 174 14 122 s rot/τ(co 2 )/ 157 166 τ(cβcγ) 13 107 sh τ(cβcγ) 151 154 12 - - τ(cβcγ)/ 130 144 11 - - rot/ 126 124 10 - - τ(cαcβ)/rot/ 109 114 9 - - rot 113 103 8 - - rot/τ(cβcγ) 102 101 7 - - /rot 98 96 6 - - 90 89 5 - - /rot 86 81 4 - - τ(cαcβ)// 69 67 rot 3 - - 64 64 2 - - 75 49 1 - - 43 40 26

Table S24: Far infrared experimental frequencies and intensities, assignments, and groups of calculated mode frequencies and symmey, for L-isoleucine zwitterion. exp. calc. freq. nb. freq. int. assign. A B 44 - - ρ(cγ1h 2 ) 751 751 43 - - ω(co 2 ) 731 731 42 - - δ(co 2 ) 702 704 41 674 m δ(co 2 )/δ(ncαc) 661 662 40 492 w,b τ(nh + 3 ) 565 565 39 492 w,b τ(nh + 3 ) 556 553 38 555 m ρ(co 2 )/δ(ncαcβ) 544 547 37 535 s ρ(co 2 )/ν(cαc) 525 525 36 492 w,b δ(cαcβcγ2) 474 473 35 441 s δ(cγcβcγ) 436 438 34 441 s δ(cγcβcγ) 432 434 33 425 m δ(cαcβcγ2) 414 416 32 389 s δ(cγcβcγ)/δ(ncαcβ) 388 392 31 368 m δ(cβcγ1cδ)/δ(ncαcβ) 360 366 30 339 s ρ(co 2 )/δ(ncαc) 343 347 29 - - δ(cβcγ1cδ)/δ(cαcβcγ2) 337 338 28 311 m δ(ncαc)/δ(cγcβcγ)/ 310 314 δ(ncαcβ) 27 - - τ(cγ2h 3 )/δ(ncαc)/ 306 303 ρ(co 2 ) 26 292 vw δ(cαcβcγ1) 282 291 25 236 s,b τ(cγ2h 3 ) 271 271 24 226 sh δ(ccαcβ) 248 257 23 206 vw δ(ccαcβ) 240 236 22 - - τ(cδh 3 )/δ(ccαcβ) 234 242 21 186 sh τ(co 2 ) 228 227 20 - - τ(cδh 3 )/τ(cγ2h 3 ) 224 222 19 173 s τ(cδh 3 ) 217 213 18 - - τ(co 2 )/τ(cδh 3 ) 210 215 17 - - τ(cγ2h 3 ) 200 201 16 - - τ(co 2 ) 183 193 15 141 s rot 168 177 14 - - rot 172 168 13 118 sh τ(cβcγ1) 158 161 12 - - τ(cβcγ1) 139 138 11 - - τ(cαcβ) 124 128 10 - - rot 130 119 9 - - 116 122 8 - - rot 121 114 7 - - rot// 110 105 τ(cαcβ) 6 - - 98 96 5 - - rot/ 95 101 4 - - /rot 96 83 3 - - 74 73 2 - - 27 31 1 - - 67-0 27

Intensity ((D/Å) 2 /u) 10 8 6 4 2 0 700 δ(co 2 ) 600 τ(nh 3 + ) 608 ω(co 2 ) 521 Wavenumber (cm 1 ) 500 400 ρ(co 2 ) δ(ncαc) 354 483 377 300 200 100 rot rot rot τ(co 2 ) 153 181 207 CALC glycine beta zwitterion EXP glycine ph6.6 (scaled) 61 0 Figure S2: Experimental (blue) and calculated (red) infrared speca for glycine β. Experimental band center frequencies are labelled. Calculated modes are annotated with the vibrations conibuting the most to the potential energy disibution. 28

Intensity ((D/Å) 2 /u) 15 10 5 0 700 δ(co 2 ) τ(nh 3 + ) 600 ω(co 2 ) 606 523 Wavenumber (cm 1 ) 500 400 ρ(co 2 ) δ(ncαc) 500 352 300 200 100 rot rot τ(co 2 ) rot 227 134 194 165 CALC glycine alpha zwitterion EXP glycine powder (scaled) 62 0 Figure S3: Experimental (blue) and calculated (red) infrared speca for glycine α. Experimental band center frequencies are labelled. Calculated modes are annotated with the vibrations conibuting the most to the potential energy disibution. 29

Intensity ((D/Å) 2 /u) 20 15 10 5 0 700 δ(co 2 H) 638 600 ω(co 2 H) 500 ρ(co 2 H) 497 400 300 200 100 Wavenumber (cm 1 ) τ(nh 3 + )/νa (Cl HN) δ(ncαc) ν s (Cl HN) ν s (Cl HN)/τ(CO 2 ) rot/ν(cl HO) τ(co 2 H)/τ(NH 3 + ) rot/ν a (Cl HN) ν(cl HO)/τ(CO 2 H)/rot rot 89 78 296 148 166 CALC glycine cation Cl EXP glycine ph1.1 (scaled) 0 Figure S4: Experimental (blue) and calculated (red) infrared speca for glycine cation. Experimental band center frequencies are labelled. Calculated modes are annotated with the vibrations conibuting the most to the potential energy disibution. 30

Intensity ((D/Å) 2 /u) 25 20 15 10 5 0 700 δ(co 2 ) 677 600 ω(co 2 ) 580 ν(ona + ) 500 rot/δ(cona + ) ν(cona + )/δ(cona + ) 513 400 300 200 100 Wavenumber (cm 1 ) rot/τ(cona + ) τ(nh 2 ) δ(ncαc)/ρ(co 2 ) /δ(cona + ) τ(co 2 )/rot τ(cona + ) τ(co 2 )/rot /rot 446 376 311 256 131 114 163 211 CALC glycine anion Na + EXP glycine ph13.0 (scaled) /rot 0 Figure S5: Experimental (blue) and calculated (red) infrared speca for glycine anion. Experimental band center frequencies are labelled. Calculated modes are annotated with the vibrations conibuting the most to the potential energy disibution. 31

Intensity ((D/Å) 2 /u) 12 10 8 6 4 2 0 ω(co 2 ) 700 δ(co 2 )/δ(ncαc) 648 600 τ(nh 3 + ) ρ(co 2 ) 539 486 500 400 300 200 100 Wavenumber (cm 1 ) δ(ncαcβ) δ(ncαc)/ρ(co 2 ) δ(ccαcβ) τ(cβh 3 ) rot τ(co 2 ) rot rot 79 109 324 259 278 221 173 292 201 409 CALC Lalanine zwitterion EXP Lalanine ph6.5 (scaled) 0 Figure S6: Experimental (blue) and calculated (red) infrared speca for L-alanine. Experimental band center frequencies are labelled. Calculated modes are annotated with the vibrations conibuting the most to the potential energy disibution. 32

Intensity ((D/Å) 2 /u) 6 4 2 0 δ(co 2 ) 700 ω(co 2 ) δ(co 2 ) δ(ncαc)/δ(co 2 )/ω(co2 ) 663 600 τ(nh 3 + ) τ(nh 3 + ) ρ(co 2 ) ρ(co 2 ) 540 500 400 300 200 100 Wavenumber (cm 1 ) δ(cαcβcγ) δ(ncαcβ) δ(ncαcβ) δ(cγcβcγ) δ(cαcβcγ) δ(cγcβcγ) δ(ncαc)/ρ(co 2 ) δ(cαcβcγ) δ(ncαc)/ρ(co 2 ) δ(ccαcβ) τ(cγh 3 ) δ(cαcβcγ)/δ(ccαcβ) τ(cγh 3 )/δ(cαcβcγ)/τ(co 2 ) τ(cγh 3 ) τ(cγh 3 ) τ(co 2 ) τ(cαcβ)/τ(cγh 3 ) τ(co 2 ) τ(cγh 3 )/rot rot τ(cαcβ) rot/τ(cαcβ) rot rot τ(cαcβ)/rot /rot 76 56 495 472 440 121 96 427 399 29279 228 218 374 333 180 145 CALC Lvaline zwitterion EXP Lvaline ph6.3 (scaled) 0 Figure S7: Experimental (blue) and calculated (red) infrared speca for L-valine. Experimental band center frequencies are labelled. Calculated modes are annotated with the vibrations conibuting the most to the potential energy disibution. 33

Intensity ((D/Å) 2 /u) 10 8 6 4 2 0 ω(co 2 ) ω(co 2 ) 700 δ(co 2 ) δ(co 2 ) 668 600 τ(nh 3 + ) τ(nh 3 + ) ρ(co 2 ) ρ(co 2 ) Wavenumber (cm 1 ) 500 400 300 200 100 δ(cδcγcδ) δ(cδcγcδ) δ(cβcγcδ) δ(cβcγcδ) δ(cβcγcδ) δ(cβcγcδ) δ(ncαc)/ρ(co 2 ) δ(cδcγcδ)/ρ(co 2 )/δ(ncαcβ) δ(cδcγcδ)/δ(ncαcβ)/δ(cβcγcδ) δ(ncαc)/ρ(co 2 ) δ(ccαcβ)/τ(cδh 3 ) τ(cδh 3 )/δ(ccαcβ) δ(cαcβcγ)/rot τ(cδh 3 ) τ(cδh 3 )/δ(cαcβcγ) τ(cδh 3 )/δ(ccαcβ) τ(cδh 3 ) τ(cδh 3 ) τ(co 2 ) τ(co 2 ) τ(co 2 )/τ(cαcβ) δ(cαcβcγ)/τ(cαcβ) rot/τ(co 2 )/τ(cβcγ) τ(cβcγ) τ(cβcγ)/ rot/ τ(cαcβ)/rot/ rot rot/τ(cβcγ) /rot /rot τ(cαcβ)//rot 504 456 73 402 534 442 203 343 330 223 364 170 122 53 138 107 CALC Lleucine zwitterion EXP Lleucine ph6.4 (scaled) 0 Figure S8: Experimental (blue) and calculated (red) infrared speca for L-leucine. Experimental band center frequencies are labelled. Calculated modes are annotated with the vibrations conibuting the most to the potential energy disibution. 34