The α-helix to β-sheet transition in poly(l-lysine): Effects of anesthetics and high pressure

Chiou, Jang-Shing; Tatara, Tsuneo; Sawamura, Seiji; Kaminoh, Yoshiroh; Kamaya, Hiroshi; Shibata, Akira; Ueda, I.

doi:10.1016/0167-4838(92)90394-s

Cited by 44 publications

(24 citation statements)

References 37 publications

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“…The same set of numerical results was compared with experimental data obtained on vimentin filaments by single-molecule AFM, 100 and Young's modulus in the range 380-540 MPa was obtained with both methods. It should be mentioned that these values are closer to those measured macroscopically on densely crosslinked IFs such as hard keratin (on the order of 1000-1500 MPa) than those obtained on more extensible egg case membranes (40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50) MPa in the a-helical domain) 42,44,101 (Fig. 5).…”

Section: Computer and Analytical Modelingsupporting

confidence: 65%

“…Hence eqn (19) was used to estimate the enthalpy change of the phase transition, DH, which provided a value comparable to calorimetric experiments used to quantify the a-b transition of poly-lysine. 46 3.1.4 Fibrin. Fibrin fibres and gels have been investigated on the macroscopic level for many decades, 47,48 with the goal of elucidating their mechanical characteristics, determining how they act to stem blood flow, and understanding how they provide adequate elasticity to blood clots.…”

Section: Macroscopic Elasticity and Phase Transitionmentioning

confidence: 99%

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Phase transition-induced elasticity of α-helical bioelastomeric fibres and networks

Miserez

Guerette

2013

Chem. Soc. Rev.

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Natural elastomeric fibres play central structural and functional roles in a variety of tissues produced by many organisms from diverse Phyla. Most of these fibres feature amorphous structure and their long-range elastic response is well described within the framework of entropic (rubber-like) elasticity. Recently, it has been recognized that long-range reversible deformation can also occur in biomacromolecular fibres or networks that feature significant secondary structure and long-range order. Their elastomeric response is then associated with conformational changes of the backbone of the constitutive protein-based polymers. Under axially imposed loads, several groups of proteins whose structure is dominated by α-helical coiled-coil structures can undergo unfolding transitions and secondary structure transformations, for example from coiled-coil α-helices to β-sheet strands. In contrast to rubber-like biopolymers, the retractive elastic force in these biomacromolecular materials is not dominated by a return to a maximum entropic state, but is mostly the result of variations in internal energy associated with the conformational changes. Here, a review of α-helix based elastomeric materials is presented that encompasses examples and experimental evidence across multiple length scales, from the molecular to the macroscopic scale. We begin by summarizing the basic thermodynamic formalism of thermoelasticity. While this formalism is well established for amorphous (entropically-dominated) fibres under tensile loading, its extension towards conformational (internal energy-dominated) elasticity is less known. Recent experimental evidence as well as corroborating computer simulations are then reviewed and discussed in the light of secondary structure and nano-scale features of these biopolymers. Comparisons are also drawn with physiologically important structural fibres that share common characteristics at the molecular and the nano-scale, including intermediate filament (IF) proteins from the cell cytoskeleton, myosins from motor proteins, and fibrin from blood clot. We conclude with a discussion on future directions and opportunities for these materials from a biomimetics engineering perspective.

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Section: Computer and Analytical Modelingsupporting

confidence: 65%

Section: Macroscopic Elasticity and Phase Transitionmentioning

confidence: 99%

Phase transition-induced elasticity of α-helical bioelastomeric fibres and networks

Miserez

Guerette

2013

Chem. Soc. Rev.

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“…Circular dichroism (CD) spectroscopy has traditionally been used to gain information about the secondary structures of proteins and polypeptides in solutions. Proteins and polypeptides assume a biologically meaningful conformation by their interaction with water (Chiou et al 1992). Therefore, in solution, polypeptides exhibit diOE erent secondary structures which are in dynamic equilibrium and the proportions of each conformer present at any one time depend on the solution microenvironment.…”

Section: Resultsmentioning

confidence: 99%

Poly(L-lysine) as a model drug macromolecule with which to investigate secondary structure and membrane transport, part I: physicochemical and stability studies

Chittchang

Alur

Mitra

et al. 2002

Journal of Pharmacy and Pharmacology

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Low oral bioavailability of therapeutic peptides and proteins generally results from their poor permeability through biological membranes and enzymatic degradation in the gastrointestinal tract. Since different secondary structures exhibit different physicochemical properties such as hydrophobicity, size and shape, changing the secondary structure of a therapeutic polypeptide may be another approach to increasing its membrane permeation. Poly(L-lysine) was used as a model polypeptide. The objectives of this study were to induce secondary structural changes in poly(L-lysine) and to determine the time course over which a given conformer was retained. In addition, the hydrophobicity of each secondary structure of poly(L-lysine) was assessed. The circular dichroism (CD) studies demonstrated that the conditions employed could successfully induce the desired secondary structural changes in poly(L-lysine). The alpha-helix conformer appeared to be more stable at 25 degrees C whereas the beta-sheet conformer could be preserved at 37 degrees C. On the other hand, the random coil conformer was retained at both temperatures. Significant losses of the alpha-helix and the beta-sheet conformers were observed when the pH was reduced. The change in ionic strength did not affect any of the conformers. The octanol/buffer partitioning studies indicated that the alpha-helix and the beta-sheet conformers exhibited significantly different (P < 0.05) hydrophobicities. In conclusion, variation of pH and temperature conditions can be used to induce secondary structural changes in poly(L-lysine). These changes are reversible when the stimuli are removed. The alpha-helix and the beta-sheet conformers of poly(L-lysine) are more lipophilic than the native random coil conformer. Thus, poly(L-lysine) may represent an ideal model polypeptide with which to further investigate the effects of secondary structure on membrane diffusion or permeation.

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“…The discovery that orderly-aggregated proteins-amyloids are associated with a number of neurological conditions, such as Alzheimer's, Huntington's, Creutzfeldt-Jakob's, and Parkinson's diseases, [1][2][3] prompted an increased interest in mechanisms of the protein aggregation. The predominantly hydrophobic character 4 or the cell membrane habitat of several amyloid-forming proteins, 2 as well as model polypeptide studies 5,6 were the early indications that changing hydration plays a role in the aggregation process. The phenomenon is now deemed to be quite common, as amyloid fibrils even from genetically distant and otherwise stably-folded helical proteins were obtained.…”

Section: Introductionmentioning

confidence: 99%

Hydration and structure—the two sides of the insulin aggregation process

Dzwolak

Ravindra

Winter

2004

Phys. Chem. Chem. Phys.

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Aggregation of bovine insulin under monomer, and dimer-promoting conditions has been probed by FT-IR spectroscopy and DSC/PPC calorimetry. This approach enabled linking of characteristic aggregationhallmarking conformational events (such as partial unfolding, and subsequent refolding into aggregated b-strands) to different stages of protein hydration. Aggregation of insulin in 20% acetic acid occurs at a markedly lower temperature than in pure water and is further enhanced in the presence of charge-shielding ions (0.1 M NaCl). While acetic acid makes the protein molecule more permissive to the solvent penetration (seen as the enhanced H/D-exchange), NaCl does not have this effect. The calorimetric data reveals that, while the aggregation itself is exothermic, in the absence of the co-solvent it is preceded by an endothermic transition. In either case, the negative heat capacity changes suggest a substantial reduction in the number of water-protein contacts upon aggregation. This has been supported by pressure perturbation calorimetry, which showed a simultaneous release of water molecules bound to the protein. The aggregation of insulin appears to be driven mostly by hydrophobic interactions and, as such, involves a rearrangement of hydrophobic side-chain amino acid residues that leads to the overall reduction in number of unfavorable protein-water contacts. The study points to the intricate nature of the acetic acid effect on insulin aggregation, which is likely to involve changing the structure of the solvating water, and direct binding to the protein.

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The α-helix to β-sheet transition in poly(l-lysine): Effects of anesthetics and high pressure

Cited by 44 publications

References 37 publications

Phase transition-induced elasticity of α-helical bioelastomeric fibres and networks

Phase transition-induced elasticity of α-helical bioelastomeric fibres and networks

Poly(L-lysine) as a model drug macromolecule with which to investigate secondary structure and membrane transport, part I: physicochemical and stability studies

Hydration and structure—the two sides of the insulin aggregation process

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