Pseudopolyelectrolyte polyamino acids

Lotan, Noah

doi:10.1021/j100621a021

Cited by 12 publications

(3 citation statements)

References 3 publications

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“…5, where the assignment is based on the results of the previous investigation [16]. The resonances of all the protons observed in the spectrum of PHEG in HFPO.d 2 .20 20 are much broader than the corresponding ones in 0 20. The spectrum of ethanolamine in HFPO.d 2 .20 20 (not shown) exhibits sharp resonance lines, similar to those observed in 0 20 [16].…”

Section: Nmr Propertiesmentioning

confidence: 95%

“…Viscosity ofPHEG in HFPD.l.lH 20 The various degrees of polymerization (Table I). For comparison, similar measurements were performed in TFE, where the polymer is e-helical, i.e., of a rod-like shape [9], and in water, where the random coil conformation is obtained [9,[16][17][18].…”

Section: Nmr Propertiesmentioning

confidence: 99%

“…Among the non-ionizable poly-o-t-amino acids, the poly-N"-(w-hydroxyalkyl)-Lglutamine derivatives [8,9], having the general structure [-NH-CH(CO-)-CH 2--CH2-CO-NH-(CH2)m-OH] x-possess the unusual property of being soluble not only in a wide range of organic solvents but also in water and aqueous salt solutions. This class of polypeptides provides, therefore, an excellent basis for systematic studies of the effect of solvents and side chain structure on the conformational behaviour of polypeptide chains, and the results of some of these investigations have been presented [8][9][10][11][12][13][14][15][16][17][18][19][20] .…”

Section: Introductionmentioning

confidence: 99%

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Conformational Behaviour of Non‐Ionizable Polypeptides in Gem‐Diol: Water Solvent Systems

Lotan

Chen

Roche

1974

Israel Journal of Chemistry

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The conformation of poly‐N5‐(2‐hydroxyethyl)‐L‐glutamine (PHEG) has been investigated in hexafluoropropan‐2,2‐diol‐water mixtures. In spite of the similarity of the circular dichroism spectra obtained in some of these mixtures and in water, NMR and hydrodynamic measurements revealed that macromolecular conformations of various degrees of rigidity are present in the different solvents considered. Homologue polymers of PHEG behave in a similar manner.

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Section: Nmr Propertiesmentioning

confidence: 95%

Section: Nmr Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Conformational Behaviour of Non‐Ionizable Polypeptides in Gem‐Diol: Water Solvent Systems

Lotan

Chen

Roche

1974

Israel Journal of Chemistry

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Reverse osmosis separations of some organic and inorganic solutes in aqueous solutions using aromatic polyamide membranes

Dickson

Matsuura

Blais

et al. 1975

J of Applied Polymer Sci

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SynopsisThe reverse osmosis separations of some ethers, ketones, aldehydes, monocarboxylic acids, and inorganic salts in singlosolute (55454 ppm) aqueous solution systems using aromatic polyamide membranes have been studied at 250 psig. It was found that reverse osmosis separation was essentially a function of steric parameter for ethers, and of both polar and steric parameters for ketones, aldehydes, and alcohols. Solute separations for monocarboxylic acids passed through a minimum at a pK, value of -4.8. The values for the free-energy parameter for Li+, Na+, K+, Rb+, Cs+, and F-, C1; Br-, I-, and IOs-ions have been calculated for the polyamide membranes used. The above values for cations are negative and those for anions are positive, suggesting that the polyamide membrane surface behaves as if it is positively charged. Further, the data show that the polyamide membrane material is only about 40% as polar as that of the cellulose acetate membrane material studied earlier.

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Critique of the interpretation of the circular dichroism of unordered polypeptides and proteins

Balasubramanian

1974

Biopolymers

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The circular dichroic (CD) profile characterizing unordered polypeptide chains and denatured proteins is the subject of much current attention. Tiffany and Krimm,' and Rippon and Walton2 have suggested that the doubly dichroic CD spectrum (positive band near 218 nm and a much larger negative band near 200 nm) obtained in ionized polyL-glutamic acid [(Glu),] and in polyl-lysine [(Lys),] chains characterize not an unordered conformation (abbreviated as U), but rather a conformation that contains regions of left-handed 31 helical order called the extended helix (abbreviated as EH). This conformational assignment was based on the similarity of this doubly dichroic CD profile with that of the polyL-proline I1 helix. Potential energy calculations, including ionic terms, on ionized (G~u),,~*( and also on ionized (Gl~-Ala),~ have yielded conformational minima for these ionized polymers at (+, $ ) 6 = 84O, 321", and 74O, 343", respectively, compared to the value 103", 326' for the polypropline I1 helix. These similarities in conformational parameters and CD spectra have led Rippon and Walton2 to conclude that the presence of a positive Cotton effect near 218 nm and a negative one near 200 nm is diagnostic of a polypeptide with 31 helical segmental order, i.e., the E H conformation.On the other hand, several workers'-9 have argued thqt the EH-type CD spectra are in fact representative of unordered structures, and that "much or all the CD data of Tiffany and Krimm may be interpreted fts mixtures of helical and unordered forms, and will not require invocation of a third structural form."8 We had observed earlier9 the ubiquity of the doubly dichroic CD spectra in a variety of polypeptides, both ionized and nonionic, under a variety of conditions. That such EH-type spectra might arise in diverse situations such as charge repulsions, protonation, or solvent binding has been claimed recently by Tiffany and Krirnm.lo However, in two recent important papers, Miller et al." have shown that under the conditions of residual blocking groups, concentration, and ionic strength of the medium, (Glu), is indeed not in the E H form, but is a random coil.Additional credence for the latter point of view is provided by the circular dichroic spectra of poly-&taspartic acid and poly-7-bglutamic acid that we present in Figure 1. These two polymers are variants of the usual poly-a-peptide sequence in that the former has an extra methylene group in the primary structural backbone, while poly-y-bglutamic acid has two methylene groups. Yet, as the figure reveals, both poly-8-lraspartate and poly-y-bglutamate display doubly dichroic spectra similar to those seen in ionized (Glu), or (Lys),. (The CD spectra of the acid forms of these two poly-w-peptides are interpreted in terms of a third Cotton effect, induced on the carboxylic acid chromoph0re.12,'~) Qualitatively similar CD spectra are exhibited by ionized copoly-(ybGluyaminobutyric acid),14 and also by the tertiary butyl esters of both these poly-w-amino acids in hexafluoroisopropanol. The additi...

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Pseudopolyelectrolyte polyamino acids

Cited by 12 publications

References 3 publications

Conformational Behaviour of Non‐Ionizable Polypeptides in Gem‐Diol: Water Solvent Systems

Conformational Behaviour of Non‐Ionizable Polypeptides in Gem‐Diol: Water Solvent Systems

Reverse osmosis separations of some organic and inorganic solutes in aqueous solutions using aromatic polyamide membranes

Critique of the interpretation of the circular dichroism of unordered polypeptides and proteins

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