Circular dichroism of the “random” polypeptide chain

Tiffany, M. Lois; Krimm, Samuel

doi:10.1002/bip.1969.360080306

Cited by 288 publications

(138 citation statements)

References 18 publications

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“…All measurements were obtained at 0". creased by raising the temperature or by addition of neutral salts and increased by lowering the temperature or by addition of denaturants, such as urea or guanidinium chloride (Tiffany & Krimm, 1969, 1973Drake et al, 1988). These denaturants are thought to increase the fractional PI1 population by hydrogen bonding preferentially with its peptide backbone (Lee & Timasheff, 1974;Siligardi & Drake, 1995).…”

Section: Discussionmentioning

confidence: 99%

The role of PII conformations in the calculation of peptide fractional helix content

1997

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Changes in the temperature, pH, ionic strength, or denaturant concentration of aqueous solutions of the monomeric non-a-helical peptide acetylYEAAAKEAPAKEAAAKAamide generate changes in its dichroic spectrum characteristic for a conformational transition. This transition has the characteristic features of a residue PII/unstructured conformational equilibrium in which PII denotes an extended left-handed helical conformation and unstructured denotes all the remaining conformations in a random coil ensemble. Replacement of the proline residue facilitates population of residues in an a-helical conformation. However, the elliptcity values for these non-proline peptides merge with the ellipticity of the proline peptide as the population of residues in the a-helix conformation is diminished. This convergence suggests that all residues in a host/guest peptide series of the same length share a common PII/unstructured conformational equilibrium in a given solvent. We propose that the fractional helix content of peptides within such a series may be estimated by using a two-state calculation in which the ellipticity for the non-a-helix conformations is provided by a peptide having a central proline guest residue.Keywords: ellipticity; helix content; peptide; PI1 conformation; random coil A variety of studies has examined the effect of a guest amino acid residue on the helical content of a host peptide of defined sequence (e.g., O'Neil & DeGrado, 1990;Lyu et al., 1990Lyu et al., , 1993Forood et al., 1993;Park et al., 1993; Chakrabarrty et al., 1994;Doig & Baldwin, 1995;Munoz et al., 1995). Such studies have been used to rank order the apparent helix propensity of the 20 common amino acid residues and to generate residue statistical parameters for prediction of helical content from sequence.We have utilized the sequence acetylYEAAAKEAXAKEAA AKAamide to synthesize a series of host/guest peptides, each containing a different guest residue X at sequence position 9 (Merutka et al., 1990;Park et al., 1993). These host/guest peptides generate a nested set of dichroic spectra having an isodichroic point at 203 nm and -16,500 deg cm2 dmol" at pH 7 and 0". The alanine 9 guest peptide has the most negative ellipticity at 222 nm, -24,300 deg cm2 d m o l~ I , and a dichroic spectrum characteristic for peptide solutions having a high fractional population of residues in the helical conformation. The proline 9 guest peptide has the least negative ellipticity at 222 nm, +I20 deg cmz dmol", and a dichroic spectrum characteristic for a random coil conformation.The proline 9 guest peptide was used subsequently to measure the effects of a variety of denaturing solvent conditions on the dichroic spectrum of a random coil. We were surprised to observe Reprint requests to: Earle Stellwagen, Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242; e-mail: cmdste@blue.weeg. uiowa.edu. that these solvent conditions generated a nested set of dichroic spectra characteristic for a conformational transition. We suggest that these dic...

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Section: Discussionmentioning

confidence: 99%

The role of PII conformations in the calculation of peptide fractional helix content

1997

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“…c-PGA conformation is sensitive to small changes in specific factors, e.g. changes in PGA side-chain ionization can have a pronounced effect on the conformation Tiffany & Krimm, 1969;Bhat, 2012).…”

Section: Conformation and Enantiomeric Composition Ofmentioning

confidence: 99%

Poly-γ-glutamic acid: production, properties and applications

et al. 2015

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“…The third aspect of protein structure analysis by CD spectroscopy is that many proteins including bovine HF (39) (35,36). These conditions produce only weak negative optical activity above about 215 nm and a weak negative CD trough around 195 nm.…”

Section: Introductionmentioning

confidence: 99%

The Secondary Structure of Human Hageman Factor (Factor XII) and its Alteration by Activating Agents

McMillin¹,

Saito²,

Ratnoff³

et al. 1974

J. Clin. Invest.

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A B S T R A C T Hageman factor (factor XII) is activated by exposure to surfaces such as glass or by solutions of certain compounds, notably ellagic acid. Changes in the structure of Hageman factor accompanying activation have been examined in this study by circular dichroism spectroscopy. The spectrum of unactivated Hageman factor in aqueous solutions suggests that its conformation is mainly aperiodic. Various perturbants altered the conformation of Hageman factor in differing ways, demonstrating the sensitivity of Hageman factor to its environment.After activation of Hageman factor with solutions of ellagic acid, a negative trough appeared in the region of the circular dichroism spectrum commonly assigned to tyrosine residues, along with other minor changes in the peptide spectral region. Some of these changes are similar to changes that occurred upon partial neutralization of the basic residues at alkali pH. Activation of Hageman factor by adsorption to quartz surfaces (in an aqueous environment) also produced changes similar to those in the ellagic acid-activated Hageman factor, including the negative ellipticity in the tyrosine region.These observations suggest that the activation process may be related to a change in status of some of the basic amino acid residues, coupled with a specific change in the environment of some tyrosine residues. The importance of these changes during the activation process remains to be determined. The

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Circular dichroism of the “random” polypeptide chain

Cited by 288 publications

References 18 publications

The role of PII conformations in the calculation of peptide fractional helix content

The role of PII conformations in the calculation of peptide fractional helix content

Poly-γ-glutamic acid: production, properties and applications

The Secondary Structure of Human Hageman Factor (Factor XII) and its Alteration by Activating Agents

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