Chemical Biology & Drug Design

Hollosi, Miklos; Wieland, Theodor

doi: 10.1111/j.1399-3011.1977.tb02805.xpmid: 604283

Ion binding properties of antamanide‐like cyclopeptides cyclo‐(Pro2–Glyn‐Pro2–Glym) (n, m = 1–3) have been studied by CD spectroscopy and by conductivity measurements. Cyclo‐(Pro2–Gly‐Pro2–Gly) forming complexes of different stoichiometry can be characterized by a strong preference of selectivity for Mg++ and Ca++ ions over alkali ions whereas the other members of the series bind selectively alkali and alkaline earth cations with ion radius of about 1 Å. Three main types of CD spectra of cyclic peptides and their complexes can be differentiated. Type I showing two negative Cotton effects at around 220 nm and 200 nm (Ib, Fig. 3), type II showing a positive band around 220 nm and a strong negative one below 190 nm (e.g. Ic in acetonitrile, Fig. 4), and type III showing a strong negative band in the 205 nm region (e.g. metal complexes of Id, Fig. 6).

Einarsson, Roland

doi: 10.1111/j.1399-3011.1977.tb02806.xpmid: 24016

Iodide is an efficient quencher of antithrombin III intrinsic tryptophan fluorescence. The quenching pattern indicates that about 60% of the tryptophyl fluorescence originates from exposed residues in the multitryptophan‐containing protein. In denaturing media all of the tryptophyls are solvent‐exposed. The binding of heparin to antithrombin III influences the number of solvent‐exposed tryptophan residues. By studying the dependence of the quenching on pH, information regarding the presence of charged residues adjacent to tryptophyls was obtained.

Treiber, L. R.; Wong, W. Mai; Shen, M. E.; Walton, Dr.A. G.

doi: 10.1111/j.1399-3011.1977.tb02807.xpmid: N/A

A polyheptapeptide poly (Ala‐Leu‐Lys‐Glu‐Ala2‐Glu) has been synthesized by polymerization of the blocked heptamer and by sequential synthesis. The former method yields molecular weights up to 40, 000, the latter a product of rather uniform D.P = 25, i.e. a molecular weight Mr= 18, 250. The polypeptide was designed to have a repeat sequence of hydrophobic residues of the type expected in α‐keratin and in tropomyosin and was designed to optimize hydrophobic bonding between two chains.

Holladay, Leslie A.; Puett, David

doi: 10.1111/j.1399-3011.1977.tb02808.xpmid: 604285

The conformations of porcine somatotropin and human choriomammotropin have been studied using circular dichroism (CD) and the results compared with spectra of human, murine, ovine, and bovine somatotropin. The far ultraviolet CD spectra of the six proteins were similar, and each spectrum was analyzed using constrained linear least squares. The following average percentages of α‐helicity, β‐structure, and aperiodic (nonhelical) conformation were obtained: 57, 6, and 37, respectively, based on a standard protein reference set, and 42, 22, and 36, respectively, based on poly‐L‐lysine as reference. Thus, the estimated secondary structure is strongly dependent upon the reference data used. Interestingly for these similar proteins, it appears that over 60% of the residues are part of ordered secondary structure and less than 40% are in an aperiodic conformation. The near ultraviolet CD spectra of these hormones were similar in many respects, although certain significant differences were observed, particularly in the sign of various extrema. These spectral differences probably reflect non‐identical microenvironments of the aromatics and disulfides, arising from differences both in amino acid sequence and local conformation.

Shopova, Maria; Genov, Nicolay

doi: 10.1111/j.1399-3011.1977.tb02809.xpmid: 24017

The photosensitized oxidation of alkaline mesentericopeptidase in the presence of methylene blue results in a first‐order rate of inactivation. The loss of enzymatic activity towards casein and N‐acetyl‐L‐tyrosine ethyl ester closely correlates with the destruction of one histidyl residue. A pK value of 6.8 is determined from the sigmoid pH‐dependence of the photoinactivation rate. This suggests the involvement of a normal titrating imidazole group in the active site of mesentericopeptidase. The competitive inhibitor Nα‐benzoyl‐L‐arginine protects the enzyme from photoinactivation. A conclusion is made that the active site histidyl residue is modified.

Bodanszky, Miklos; Fagan, Daniel T.

doi: 10.1111/j.1399-3011.1977.tb02810.xpmid: 604286

The imidazole catalyzed transesterification of active esters was used for the formation of the ester bond between the carboxyl group of protected amino acids and the hydroxyl group of a polymeric support applied in solid phase peptide synthesis. Anchoring of the C‐terminal residue to the hydroxymethyl polymer proceeded smoothly and provided a high degree of incorporation. No racemization was observed in the imidazole‐catalyzed alcoholysis. The procedure could be carried out with various active esters such as esters of o‐ and p‐nitrophenol, 2, 4, 5–trichlorophenol, pentachlorophenol and N‐hydroxysuccinimide.

Bodanszky, Miklos; Tolle, John C.

doi: 10.1111/j.1399-3011.1977.tb02811.xpmid: N/A

Acylation of amino acid β‐naphthylamides with protected (Boc) amino acid‐isobutylcarbonic acid mixed anhydrides resulted in each case in the formation of some undesired by‐product: an isobutyloxycarbonylamino acid β‐naphthylamide. The amount of this second acylation product was particularly high, with the hindered amino acids valine and isoleucine as carboxyl‐components. The nature of the amino component had no major influence on the extent of this side reaction.

Noble, Richard L.; Yamashiro, Donald; Li, Choh Hao

doi: 10.1111/j.1399-3011.1977.tb02812.xpmid: N/A

The amino terminal 54 residue peptide fragment of human somatotropin, [Cys(Cam)53]‐HGH‐(I‐54), has been synthesized by the solid‐phase method. The symmetrical anhydride and active ester coupling methods were used exclusively. The synthetic product was purified by gel filtration, isoelectric focusing, and partition chromatography. It was found to be homogeneous by six additional criteria.

doi: 10.1111/j.1399-3011.1977.tb02813.xpmid: N/A