ACTA CHIMICA SINICA. . NaCl > KCl > LiCl, KCl > LiCl > NaCl. , KCl

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1 ACTA CHIMICA SINICA Vol No : Ξ a b a KNIGHT David P b VOLLRATH Fritz b Ξ ( a ) ( b OX1 3PS ) NaCl > KCl > LiCl 2 KCl > LiCl > NaCl KCl ( ) ( 5 min ) ( 50 min ) Conformation Transition of Silk Protein Membranes Monitored by Time2resolved FTIR Spectroscopy : Effect of Alkali Metal Ions on Nephila Spidroin Membrane CHEN Xin Ξ a b SHAO Zheng2Zhong a KNIGHT David P b VOLLRATH Fritz b ( a Department of Macromolecular Science Key Laboratory of Molecular Engineering of Polymers of Education Ministry Fudan University Shanghai ) ( b Department of Zoology University of Oxford South Parks Road Oxford OX1 3PS UK) Abstract The conformation transition processes of Nephila spidroin membranes induced by alkali salt solutions were monitored by time2resolved FTIR spectroscopy Though the transition rate of spidroin in the membrane was NaCl > KCl > LiCl the 2sheet structure content in the membrane ( after the conformation transition completed) was KCl > LiCl > NaCl Comparing the transition rate and final 2sheet structure content in the membrane KCl has the best effect in inducing the conformation transition of spidroin membrane among the three alkali salts we used This supports the assumption that the K + ions play an important role in the spinning process of spiders In the meantime the conformation transition process was indicated to have two intermediate states that contain different levels of 2sheet structure The first phase (fast phase with a time constant of 5 min) was assigned to the 2sheet formation by segments movement while the second phase ( slow phase with a time constant of 50 min) was attributed to the whole macromolecular rearrangement Keywords time2resolved FTIR spectroscopy Nephila spidroin membrane conformation transition kinetics Ξ E2mail : edu cn ; Fax : Received May ; revised August ; accepted August (No ) Biotechnology and Biological Sciences Research Council (BBSRC) Engineering and Physical Sciences Research Council ( EPSRC)

2 2204 Vol alkali spinning mechanism K + ( dragline) 1 Kevlar [1] 1 1 [18 ] [2 4 ] ( Nephila senegalensis) ph 8 2 Ringer (major ampullate) Ringer (spidroin dope) ( ) 2 w = 2 % 1 ml 3 cm 3 cm (25 [1 5 6] [7 ] 50 % ) ( 24 h) 5 m 1 2 / ( ) 25 Nicolet Magna 550 [8 9 ] [10 11] [12] JUN2AIR Peak Scientific MCT cm - 1 [13 ] 3 mm 6 mm 100 m 1 0 mol/l ( [14 16 (folding) ] Aldrich) (128 ( Na + K + ) 4 cm - 1 ) K + [17 ] 0 58 min K min (nanofibrils) ( difference spectra) : [18] [19 ] t K + ( 10 mmol/ L 1 0 mol/ L) (240 min ) K + t 1 0 mol/ L (Li + Na + K + ) Microcal TM Origin TM 5 0 ; PeakFit TM 4 1 ( SPSS Inc )

3 No 12 : ( ) 3a 3b 2a 2b I [13 ] : 2 ( 1 ( a) : I ) ( 1648 cm - 1 ) [20 23] [13 ] 1 0 mol/ L : cm cm - 1 ( 1 b) 1620 cm cm (turn) [20 23 ] [19 ] cm - 1 ( 2b) : 2 (1620 cm - 1 ) (1691 cm - 1 ) ( ) 1 (a) (b) mol/ L (a) ; (b) Figure 2 Time2resolved FTIR spectra of Nephila spidroin membranes induced by 1 0 mol/ L NaCl/ D 2 O solution (a) Normal spectra ; (b) difference spectra ( 1 0 mol/ L ) 2 2 Figure 1 FTIR spectra of Nephila spidroin membranes before (a) [13 and after (b) 19] the conformation transition occurred (induced by 1 0 mol/ L LiCl/ D 2 O solution) ( absorbance) 2a 1 0 mol/ L NaCl mol/ L 2 2 (1648 cm - 1 ) 2 (1620 cm - 1 )

4 2206 Vol mol/ L (a) ; (b) Figure 3 Three dimensional time2resolved FTIR spectra of Nephila spidroin membranes induced by 1 0 mol/ L NaCl/ D 2 O solution (a) Normal spectra ; (b) difference spectra membrane monitored by time2resolved FTIR spectroscopy (a) Increasing of 2 ( ) 1 0 mol/ L 1 0 mol/ L ( 5) ( 2 ) (second mol/ L (a) 1620 cm ; (b) 1648 cm - 1 Figure 4 Conformation transition kinetics of Nephila spidroin around 1648 cm - 1 2sheet at 1620 cm - 1 ; ( b) decreasing of random coil order exponential decay) 5 ( 1 2 ) (1620 cm - 1 ) ( 1 ) 1 Figure 5 Comparison of conformation transition kinetics of Nephila spidroin membranes induced by different alkali salt solutions ( ( ) ( 1620 cm % 1691 cm - 1 cm - 1 band) 42 %) 1 ( ) 10 % 1

5 No 12 : mol/ L a 1 Table 1 Conformation transition kinetics of Nephila spidroin membranes induced by alkali salt solutions 1620 cm / min 2 / min 1 / % 1691 cm / min 2 / min 1 / % a A ( absorbance) ( 1 ) 1 1 = A 1 / (A 1 + A 2 ) A 1 A ( ) 2 ( 5 1) [13 ] : [17 / ] ; ; (nanofibril) [18 2 ] ( ) 4 9 [24 ( ) 25] ( 24 h [26] 1 ( ) 4 h ) PeakFit TM [19 ] : 2 ( ) 2 2 ( ) ; ; ( K + / Na + [17 ) ]

6 2208 Vol Kerkam K ; Viney C ; Kaplan D ; Lombardi S Nature [7] 2 6 Willcox P J ; Gido S P ; Muller W ; Kaplan D L Macromolecules Li G Y ; Zhou P ; Shao Z Z ; Xie X ; Chen X ; 2 2 Wang H H ; Chunyu L J ; Yu T Y Eur J Biochem Table 2 2Sheet content in Nephila spidroin membranes after the 8 Lenormant H Trans Faraday Soc conformation transition induced by different alkali salts solutions 9 Hijirida D H ; Do K G ; Michal C ; Wong S ; Zax a 1 0 mol/ L 2 / % Abs 1620 / Abs 1691 D ; Jelinski L W Biophys J Shao Z ; Vollrath F ; Sirichaisit J ; Young R J Polymer Shao Z Z ; Young R J ; Vollrath F Int J Biol a Abs 1620 / Abs (1620 Macromol cm - 1 ) (1691 cm - 1 ) ( 12 Chen X ; Li W J ; Yu T Y J Polym Sci Part B : ) 3 14 Reinstadler D ; Fabian H ; Backmann J ; Naumann D Biochemistry Williams S ; Causgrove T P ; Gilmanshin R ; Fang K S ; Callender R H ; Woodruff W H ; Dyer R B 2 Biochemistry Gilmanshin R ; Williams S ; Callender 2 R H ; Mr Paul Embden 18 Chen X ; Knight D P ; Vollrath F Biomacromolecules 19 Chen X ; Kinght D P ; Shao Z Z ; Vollrath F Biochemistry 2002 in press References 1 Vollrath F ; Knight D P Nature Liivak O ; Blye A ; Shah N ; Jelinski L W Macromolecules Seidel A ; Liivak O ; Jelinski L W Macromolecules Seidel A ; Liivak O ; Calve S ; Adaska J ; Ji G D ; Yang Z T ; Grubb D ; Zax D B ; Jelinski L W Macromolecules Polym Phys Chen X ; Shao Z Z ; Marinkovic N S ; Miller L M ; Zhou P ; Chance M R Biophys Chem Woodruff W H ; Dyer R B Biochemistry Knight D P ; Vollrath F Naturwissenschaften Byler D M ; Susi H Biopolymers Surewicz W K ; Mantsch H H Biochim Biophys Acta Dong A ; Huang P ; Caughey W S Biochemistry Simonetti M ; Di Bello C Biopolymers Canetti M ; Seves A ; Secundo F ; Vecchio G Biopolymers Simmons A H ; Michal C A ; Jelinski L W Science Helfand E Science (A LI L T ; FAN Y Y )