Conformational studies of polymers and copolymers of <scp>L</scp>‐aspartate esters. I. Preparation and solution studies

Bradbury, E. Morton; Carpenter, Brian; Goldman, Howard

doi:10.1002/bip.1968.360060607

Cited by 128 publications

(70 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A novel alternative, applicable under certain conditions, may be by a helix-helix (P-M) transition driven by an external stimulus, affording almost mirror-image helical motifs. Although biochemists originally discovered this intriguing phenomenon almost three decades ago in synthetic DNA (driven by a change in salt concentration), [123] and poly(l-aspartic acid ester)s (driven by a change in temperature and organic acid), [124] very few polymers such a calf thymus DNA [125] and several artificial polymers [20 -22, 23,32, 37, 38,42, 126 -129] are known to undergo the P-M transition phenomenon driven by external stimuli. This might be a result of limited scientific knowledge and understanding of the nature of P-M transition characteristics.…”

Section: Thermo-driven Helix-helix Transitionmentioning

confidence: 99%

Optically Active Polysilylenes: State-of-the-Art Chiroptical Polymers

Fujiki

2001

Macromol. Rapid Commun.

271

204

View full text Add to dashboard Cite

Section: Thermo-driven Helix-helix Transitionmentioning

confidence: 99%

Optically Active Polysilylenes: State-of-the-Art Chiroptical Polymers

Fujiki

2001

Macromol. Rapid Commun.

271

204

View full text Add to dashboard Cite

“…7 The samples of poly(r-ethyl oglutamate) (PEDG), poly(r-n-propyl o-glutamate) (PnPDG), poly(r-n-butyl o-glutamate) (PnBDG) and poly(r-n-hexyl o-glutamate) (PnHDG) were obtained by this method. The degree of substitution of the methyl group for the n-alkyl group was evaluated by the high resolution NMR spectra (model JNM-MH-60E, Japan Electron Optics Laboratory Co., Ltd.) as shown in Figure l.…”

Section: Methodsmentioning

confidence: 99%

Aggregated States of Molecular Chains in Solid-State Films of Poly(γ-n-alkyl D-glutamate) Cast from Various Solutions

Ito

Kajiyama

Takayanagi

1977

Polym J

View full text Add to dashboard Cite

ABSTRACT:The aggregated states of molecular chains in the crystalline region were studied for well annealed films of poly(r-methyl o-glutamate) and poly(r-n-hexyl o-glutamate) cast from various solutions. These crystalline regions were found to be composed of the a-helical chains in hexagonal array by means of the X-ray diffraction technique. Both a planar and a (1010) uniplanar orientations were found in the solid films of poly(r-methyl o-glutamate), depending upon the kind of solvents and casting temperatures. Only a (1120) uniplanar orientation was observed in the solid film of poly(r-n-hexyl o-glutamate). Viscosity measurements and optical microscopic observations revealed that the aggregated states of molecular chains in the solid were in close relation to those in solutions found in the evaporating process of solvents. In the case of poly(r-methyl o-glutamate), a planar orientation was observed when a cholesteric solution was cast and dried, and also a (1010) uniplanar orientation was observed when a solution was gelatinized. On the other hand, in the case of poly(r-n-hexyl o-glutamate), a liquid crystalline state was observed in any one solvent used for this report, resulting in a (1120) uniplanar orientation in the cast film.KEY WORDS Poly(r-methyl o-glutamate) / Poly(r-n-hexyl o-glutamate) / Planar Orientation / Uniplanar Orientation / Viscosity / Cholesteric Liquid Crystal / Polarizing Micro-Photograph / There have been many investigations on the aggregated states of poly(r-benzyl L-glutamate) (PBLG) molecular chains in dilute solutions, concentrated solutions and a solid-state. Doty, et al.,1 reported that the molecular association of PBLG was of the end-to-end type in a dilute solution of chloroform, dioxane, or benzene. They also mentioned that in the dimethylformamide solution, the association of the a-helices was prevented by solvation of helix-ends with dimethylformamide molecules. Wada, et al.,2 reported that PBLG molecules existed in a dispersed state in a dilute dimethylformamide solution, whereas in a dilute solution of dimethylformamide-dioxane, associations of headto-tail and side-by-side types were formed with decreasing the concentration of PBLG. Robinson, et al.,3 reported that PBLG and poly(r-methyl L-glutamate) (PMLG) molecules formed a cholesteric liquid crystal in concentrated solutions of dioxane, m-cresol, chloroform and so on. In these solutions, the two characteristic concentrations were found, that is, the A-point above which the anisotropic phase appears and the Bpoint above which the isotropic liquid phase no longer exists. These A-and B-points depend on molecular weight. The phase separation at the A-point is predicted by Flory's theory. 4 Hermans 5 studied the viscosity-concentration relationship for a concentrated poly(r-benzyl Lglutamate) solution in m-cresol using a shear type viscometer and reported that below the Apoint, the viscosity at low shear stress increased with increasing concentration and above the A-point, it decreased with increasing concentration. Tobolsky,...

show abstract

“…Fundamentals of our three-state, nearestneighbor interaction model are selfexplanatory in eq 1. The ( l, l) and {2 , 2) elements of w having the statistical weight sh characterize the helix propagation process maintaining the same sense, while the (3, l) and (3,2) elements with uhSh characterize the helix initiation process from coil residues. In the third column the same statistical weight of unity is assigned to all coil residues irrespective of the conformational state of their preceding residues.…”

Section: Nearest-neighbor Interaction Modelmentioning

confidence: 99%

Dimensional Changes of Polypeptides in the Helix-Sense Inversion Region

Toriumi

1987

Polym J

View full text Add to dashboard Cite

ABSTRACT:Dimensional changes of polypeptides in the helix-sense inversion region are analyzed by a theory based on the three-state, nearest-neighbor interaction model. Each peptide residue in a chain is assumed to take on right-and left-handed ex-helical states as well as a random coil state, and the helix stabilization effect due to hydrogen-bond interactions is taken into account. Such interactions between four consecutive residues have explicitly been discussed in a 9 x 9 statistical-weight matrix in a previous theory [Macromolecules, 17, I 599 (1984)], while in the present model we simplify this matrix into the form of a 3 x 3 matrix by considering the interactions only between two consecutive residues. Calculations of the average helix fraction and the number of helix sequences are correspondingly simplified with maintaining quantitative agreement in numerical results. The new theory is also applied to the analyses of the length distribution and the higher moments of helix. Theoretical transition curves illustrating the general characteristics of the sense inversion phenomena suggest a method for evaluating the transition parameters.KEY WORDS Polypeptide I Helix-Sense Inversion j Chain Dimension I Nearest-Neighbor Interaction Model/ In a previous study 1 we have developed a theory of the helix-sense inversion in polypeptides for interpreting the unusual conformational transitions exhibited by poly(aspartate ester)s. For example, poly(/1-phenethyl L-aspartate) (PPELA), being in a right-handed tx-helical form (RH tx) in chloroform, undergoes a sense inversion to a lefthanded tx form (LH tx) when a small amount of denaturing solvent such as dichloroacetic acid or triftuoroacetic acid is added. 2 • The LH txhelix thus formed can then be transformed into a random coil form by further increasing the acid concentration. Moreover, PPELA in an appropriate chloroform-acid mixture undergoes a thermally induced sense inversion from RH to LH tx-helix upon heating. An indication of this latter type of inversion has also been reported for poly(/1-n-propyl L-aspartate) in chloroform. 3 · 4 Generally, the stabilities of the two tx-helical forms of poly(aspartate ester)s are known to be low and close together. 3 -8 The sense inversion can therefore be induced relatively easily in this class of polypeptides when the solution conditions are appropriately changed.In the theory in ref I (hereafter referred to as Part I) we have assumed that each peptide residue in a chain can take on three conformational states (RH tx, LH tx and coil states), and that the conformational stability of a given residue depends on the states of its neighboring three residues. This latter requirement arises since a hydrogen-bond bridge stabilizing the helix sequence forms only when three consecutive residues are cooperatively distorted to the tx-helical state of the same sense. A statistical-weight matrix representing this long-range hydrogen-bond interaction is given by a 9 x 9 matrix with five non-zero 1395 H. TORIUMI eigenvalues. The partition f...

show abstract

Conformational studies of polymers and copolymers of L‐aspartate esters. I. Preparation and solution studies

Cited by 128 publications

References 17 publications

Optically Active Polysilylenes: State-of-the-Art Chiroptical Polymers

Optically Active Polysilylenes: State-of-the-Art Chiroptical Polymers

Aggregated States of Molecular Chains in Solid-State Films of Poly(γ-n-alkyl D-glutamate) Cast from Various Solutions

Dimensional Changes of Polypeptides in the Helix-Sense Inversion Region

Contact Info

Product

Resources

About