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Structural dynamic of a self-assembling peptide d-EAK16 made of only D-amino acids.

Luo Z, Zhao X, Zhang S - PLoS ONE (2008)

Bottom Line: We compare these results with its chiral counterpart L-form, l-EAK16.Since D-form peptides are resistant to natural enzyme degradation, such drastic structural changes may be exploited for fabricating molecular sensors to detect minute environmental changes.This provides insight into the behaviors of self-assembling peptides made of D-amino acids and points the way to designing new peptide materials for biomedical engineering and nanobiotechnology.

View Article: PubMed Central - PubMed

Affiliation: West China Hospital, Laboratory for Nanobiomedical Technology, Sichuan University, Chengdu, Sichuan, China.

ABSTRACT
We here report systematic study of structural dynamics of a 16-residue self-assembling peptide d-EAK16 made of only D-amino acids. We compare these results with its chiral counterpart L-form, l-EAK16. Circular dichroism was used to follow the structural dynamics under various temperature and pH conditions. At 25 degrees C the d-EAK16 peptide displayed a typical beta-sheet spectrum. Upon increasing the temperature above 70 degrees C, there was a spectrum shift as the 218 nm valley widens toward 210 nm. Above 80 degrees C, the d-EAK16 peptide transformed into a typical alpha-helix CD spectrum without going through a detectable random-coil intermediate. When increasing the temperature from 4 degrees C to 110 degrees C then cooling back from 110 degrees C to 4 degrees C, there was a hysteresis: the secondary structure from beta-sheet to alpha-helix and then from alpha-helix to beta-sheet occurred. d-EAK16 formed an alpha-helical conformation at pH0.76 and pH12 but formed a beta-sheet at neutral pH. The effects of various pH conditions, ionic strength and denaturing agents were also noted. Since D-form peptides are resistant to natural enzyme degradation, such drastic structural changes may be exploited for fabricating molecular sensors to detect minute environmental changes. This provides insight into the behaviors of self-assembling peptides made of D-amino acids and points the way to designing new peptide materials for biomedical engineering and nanobiotechnology.

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The temperature effect on the d-EAK16 and l-EAK16 (100 µM). Each spectrum was collected at indicated temperature from 10°C to 110°C, using the same samples covered with mineral oils to prevent water evaporation. Every temperature point was averaged from 3 measurements.The sample was incubated at indicated temperatures for 15 minutes because 3 at 5-minute each measurements took 15 minutes. After measurement at 10°C, then the temperature was increased to 20°C, 30°C, 40°C, etc in the CD instrument to reach the indicated temperature and eventually elevated to 110°C. A) The CD spectra of d-EAK16 from 10°C to 110°C. At 20°C, it formed a stable beta-sheet. This beta-sheet structure was stable until 80°C. It then underwent two distinctive transitions. During the first transition, the beta-sheet content was not only reduced, but also changed its twist. The second structural transition occurs between 80°C to 90°C and drastically between 90°C to 110°C. Here, the beta-sheet structure is converted to an alpha-helical structure. B) d-EAK16 exhibits 3 distinctive structures at different temperatures, 60°C, 80°C, and 90°C. The isosbestic point was at 208nm as indicated by an arrow. C) The CD spectra of l-EAK16 from 10°C to 110°C. It was a very stable beta-sheet. The beta-sheet content was reduced, but no obvious structural transition was observed. D) l-EAK16 was very stable at different temperatures, 80°C, 90°C, 100°C and 110°C. No drastic structural transition was observed.
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pone-0002364-g003: The temperature effect on the d-EAK16 and l-EAK16 (100 µM). Each spectrum was collected at indicated temperature from 10°C to 110°C, using the same samples covered with mineral oils to prevent water evaporation. Every temperature point was averaged from 3 measurements.The sample was incubated at indicated temperatures for 15 minutes because 3 at 5-minute each measurements took 15 minutes. After measurement at 10°C, then the temperature was increased to 20°C, 30°C, 40°C, etc in the CD instrument to reach the indicated temperature and eventually elevated to 110°C. A) The CD spectra of d-EAK16 from 10°C to 110°C. At 20°C, it formed a stable beta-sheet. This beta-sheet structure was stable until 80°C. It then underwent two distinctive transitions. During the first transition, the beta-sheet content was not only reduced, but also changed its twist. The second structural transition occurs between 80°C to 90°C and drastically between 90°C to 110°C. Here, the beta-sheet structure is converted to an alpha-helical structure. B) d-EAK16 exhibits 3 distinctive structures at different temperatures, 60°C, 80°C, and 90°C. The isosbestic point was at 208nm as indicated by an arrow. C) The CD spectra of l-EAK16 from 10°C to 110°C. It was a very stable beta-sheet. The beta-sheet content was reduced, but no obvious structural transition was observed. D) l-EAK16 was very stable at different temperatures, 80°C, 90°C, 100°C and 110°C. No drastic structural transition was observed.

Mentions: A sample of 100 µM d-EAK16 was used for studying the peptide structures. Circular dichroism (CD) was used to follow the structural behaviors. The d-EAK16 peptide showed interesting structural dynamic at different temperature. The beta-sheet structure of d-EAK16 is relatively stable at low temperature up to 70°C. But, further increasing temperature resulted in an abrupt structural transition from beta-sheet to alpha-helix (Fig. 3). This observation is similar to what we have reported of other peptides [6], [7].


Structural dynamic of a self-assembling peptide d-EAK16 made of only D-amino acids.

Luo Z, Zhao X, Zhang S - PLoS ONE (2008)

The temperature effect on the d-EAK16 and l-EAK16 (100 µM). Each spectrum was collected at indicated temperature from 10°C to 110°C, using the same samples covered with mineral oils to prevent water evaporation. Every temperature point was averaged from 3 measurements.The sample was incubated at indicated temperatures for 15 minutes because 3 at 5-minute each measurements took 15 minutes. After measurement at 10°C, then the temperature was increased to 20°C, 30°C, 40°C, etc in the CD instrument to reach the indicated temperature and eventually elevated to 110°C. A) The CD spectra of d-EAK16 from 10°C to 110°C. At 20°C, it formed a stable beta-sheet. This beta-sheet structure was stable until 80°C. It then underwent two distinctive transitions. During the first transition, the beta-sheet content was not only reduced, but also changed its twist. The second structural transition occurs between 80°C to 90°C and drastically between 90°C to 110°C. Here, the beta-sheet structure is converted to an alpha-helical structure. B) d-EAK16 exhibits 3 distinctive structures at different temperatures, 60°C, 80°C, and 90°C. The isosbestic point was at 208nm as indicated by an arrow. C) The CD spectra of l-EAK16 from 10°C to 110°C. It was a very stable beta-sheet. The beta-sheet content was reduced, but no obvious structural transition was observed. D) l-EAK16 was very stable at different temperatures, 80°C, 90°C, 100°C and 110°C. No drastic structural transition was observed.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2387071&req=5

pone-0002364-g003: The temperature effect on the d-EAK16 and l-EAK16 (100 µM). Each spectrum was collected at indicated temperature from 10°C to 110°C, using the same samples covered with mineral oils to prevent water evaporation. Every temperature point was averaged from 3 measurements.The sample was incubated at indicated temperatures for 15 minutes because 3 at 5-minute each measurements took 15 minutes. After measurement at 10°C, then the temperature was increased to 20°C, 30°C, 40°C, etc in the CD instrument to reach the indicated temperature and eventually elevated to 110°C. A) The CD spectra of d-EAK16 from 10°C to 110°C. At 20°C, it formed a stable beta-sheet. This beta-sheet structure was stable until 80°C. It then underwent two distinctive transitions. During the first transition, the beta-sheet content was not only reduced, but also changed its twist. The second structural transition occurs between 80°C to 90°C and drastically between 90°C to 110°C. Here, the beta-sheet structure is converted to an alpha-helical structure. B) d-EAK16 exhibits 3 distinctive structures at different temperatures, 60°C, 80°C, and 90°C. The isosbestic point was at 208nm as indicated by an arrow. C) The CD spectra of l-EAK16 from 10°C to 110°C. It was a very stable beta-sheet. The beta-sheet content was reduced, but no obvious structural transition was observed. D) l-EAK16 was very stable at different temperatures, 80°C, 90°C, 100°C and 110°C. No drastic structural transition was observed.
Mentions: A sample of 100 µM d-EAK16 was used for studying the peptide structures. Circular dichroism (CD) was used to follow the structural behaviors. The d-EAK16 peptide showed interesting structural dynamic at different temperature. The beta-sheet structure of d-EAK16 is relatively stable at low temperature up to 70°C. But, further increasing temperature resulted in an abrupt structural transition from beta-sheet to alpha-helix (Fig. 3). This observation is similar to what we have reported of other peptides [6], [7].

Bottom Line: We compare these results with its chiral counterpart L-form, l-EAK16.Since D-form peptides are resistant to natural enzyme degradation, such drastic structural changes may be exploited for fabricating molecular sensors to detect minute environmental changes.This provides insight into the behaviors of self-assembling peptides made of D-amino acids and points the way to designing new peptide materials for biomedical engineering and nanobiotechnology.

View Article: PubMed Central - PubMed

Affiliation: West China Hospital, Laboratory for Nanobiomedical Technology, Sichuan University, Chengdu, Sichuan, China.

ABSTRACT
We here report systematic study of structural dynamics of a 16-residue self-assembling peptide d-EAK16 made of only D-amino acids. We compare these results with its chiral counterpart L-form, l-EAK16. Circular dichroism was used to follow the structural dynamics under various temperature and pH conditions. At 25 degrees C the d-EAK16 peptide displayed a typical beta-sheet spectrum. Upon increasing the temperature above 70 degrees C, there was a spectrum shift as the 218 nm valley widens toward 210 nm. Above 80 degrees C, the d-EAK16 peptide transformed into a typical alpha-helix CD spectrum without going through a detectable random-coil intermediate. When increasing the temperature from 4 degrees C to 110 degrees C then cooling back from 110 degrees C to 4 degrees C, there was a hysteresis: the secondary structure from beta-sheet to alpha-helix and then from alpha-helix to beta-sheet occurred. d-EAK16 formed an alpha-helical conformation at pH0.76 and pH12 but formed a beta-sheet at neutral pH. The effects of various pH conditions, ionic strength and denaturing agents were also noted. Since D-form peptides are resistant to natural enzyme degradation, such drastic structural changes may be exploited for fabricating molecular sensors to detect minute environmental changes. This provides insight into the behaviors of self-assembling peptides made of D-amino acids and points the way to designing new peptide materials for biomedical engineering and nanobiotechnology.

Show MeSH
Related in: MedlinePlus