Effects of solution polarity and viscosity on peptide deamidation.

Deamidation kinetics were measured for a model hexapeptide (L-Val-L-Tyr-L-Pro-L-Asn-Gly-L-Ala, 0.02 mg/mL) in aqueous solutions containing glycerol (0-50% w/w) and poly(vinyl pyrrolidone) (PVP, 0-20% w/w) at 37 degrees C and pH 10 to determine the effects of solution polarity and viscosity on reactivity. The observed pseudo-first order deamidation rate constants, k(obs), decreased markedly when the viscosity increased from 0.7 to 13 cp, but showed no significant change at viscosities >13 cp. Values of k(obs) also increased with increasing dielectric constant and decreasing refractive index. Molecular dynamics simulations indicated that the free energy associated with Asn side-chain motion is insensitive to changes in dielectric constant, suggesting that the observed dielectric constant dependence is instead related primarily to the height of the transition state energy barrier. An empirical model was proposed to describe the effects of the viscosity, refractive index and dielectric constant on k(obs). Analysis of the regression coefficients suggested that both permanent and induced dipoles of the medium affect the deamidation rate constant, but that solution viscosity is relatively unimportant in the range studied.     

Antithrombin III mRNA in adult rat liver and kidney and in rat liver during development

Using Northern blots the size of antithrombin III (AT III) mRNA in rat liver was found to be 1650 nucleotides. Adult rat kidney also contained a slightly smaller mRNA at about 20% the level in liver. The ontogeny of AT III mRNA in the liver was assessed by dot blot hybridization. The mRNA was detectable at the earliest age examined (14th day of gestation) at about 15% of the adult levels. After the 17th day of gestation the levels of antithrombin III mRNA rise reaching 50% of adult levels at birth. After birth the mRNA levels rise to 75% of adult levels by the 5th day and reach adult levels by 40 days after birth. We suggest that foetal AT III is produced by both the foetal liver and by placental transfer of the maternal inhibitor.     

A rapid method for the purification of D-amino acid oxidase of Trigonopsis variabilis by hydrophobic chromatography

Summary A relatively simple method has been described for the rapid purification of D-amino acid oxidase from Trigonopsis variabilis by hydrophobic chromatography on Phenyl-Sepharose CL-4B and negative adsorption on DEAE-cellulose. The purified enzyme had a specific activity of 22–24 units at 25°C and exhibited three bands on enzymatic staining.     

Algal Carotenoids 51. Secondary carotenoids 2.Haematococcus pluvialis aplanospores as a source of (3S, 3′S)-astaxanthin esters

Aplanospores ofHaematococcus pluvialis MUR 145 contained 0.7% carotenoids (dry wt. basis) consisting of β,β-carotene (5% of total carotenoid), echinenone (4%), canthaxanthin (4%), (3S,3′S)-astaxanthin diester (34%), (3S,3′S)-astaxanthin monoester (46%), (3S,3′S)-astaxanthin (1%) and (3R,3′R,6′R)-lutein (6%). The astaxanthin esters were examined by TLC and HPLC and VIS,¹H NMR and mass spectra recorded. Their chirality was determined by the camphanate method (Vecchi & Müller, 1979) after anaerobic hydrolysis. The tough cell wall of the aplanospores required enzymatic treatment prior to pigment extraction. The potential use of this microalga as a feed ingredient in aquaculture is discussed briefly.     

Correction of the published sequence for the human proteolipid protein gene

Summary In the human proteolipid protein gene, the base sequence of the intronic region 5 to exon 6 was found to be 5-ctctttcattttcctgcag-3 and not 5-ctctttt-cattttcctgcag-3 as previously reported.     

Hydrolysis of milk lactose by immobilized beta-galactosidase-hen egg white powder

Immobilized beta-galactosidase was obtained by crosslinking the enzyme with hen egg white using 2% glutaraldehyde. The gel obtained could be lyophilized to give a dry enzyme powder. The pH optimum of both the soluble and immobilized enzyme was found to be 6.8. The immobilized enzyme showed a higher K(m) for the substrates. The extent of enzyme inhibition by galactose was reduced upon immobilization. The stability towards inactivation by heat, urea, gamma irradiation, and protease treatment were enhanced. The bound enzyme as tested in a batch reactor could be used repeatedly for the hydrolysis of milk lactose. The possible application of this system for small-scale domestic use has been suggested.     

Immobilization of fumarase by entrapment of rat liver mitochondria in polyacrylamide gel using gamma rays

A stable immobilized preparation of fumarase (EC 4.2.1.2) was obtained by entrapment of rat liver mitochondria in acrylamide polymerized by using gamma irradiation (100 kR). The enhanced stability and the efficiency of the entrapped enzyme have shown potential for repeated use for the production of L-malic acid from fumaric acid. The possible formation of succinic acid in the system could be controlled by incorporating malonate along with detergents such as sodium deoxycholate or sodium dodecylsulfate in the reactor system.     

A simplified procedure for cDNA and genomic library construction using nonpalindromic oligonucleotide adaptors

The properties and characteristics of oligonucleotide adaptors for use in a simplified procedure for the construction of cDNA and genomic DNA libraries are described. The adaptors are suitable for joining to blunt ended cDNA or sheared genomic DNA, and then to the cohesive ends of restriction sites in vectors. Each adaptor consists of two oligonucleotides with complementary but nonpalindromic sequences that include an internal restriction site, a 5' phosphorylated blunt end, and an overlapping or staggered 5' hydroxylated end corresponding to a restriction endonuclease site in a vector of choice. Ligation of the blunt end to high molecular weight target DNA proceeds efficiently and there is no tandem concatenation of the adaptor. Insertion into the appropriate vector only requires ligation of the cohesive ends. There is no requirement for methylation, restriction enzyme cleavage, G-C tailing, or denaturation after ligation of the adaptor to the target DNA, all characteristics of other procedures.     

Isolation and characterization of a platelet membrane protein related to the vitronectin receptor

Glycoprotein IIb-IIIa is the most prominent Arg-Gly-Asp (RGD)-binding adhesion receptor on platelets. By affinity chromatography on an immobilized RGD peptide, we have investigated the possible existence of other platelet-associated adhesion receptors that bind RGD peptides. When an octyl glucoside extract of surface-radioiodinated platelets was applied to an affinity matrix of KYGRGDS-coupled Sepharose 4B, a 160-kDa-labeled protein (P160) and GPIIb-IIIa bound and were specifically eluted by soluble GRGDSP peptide, but not by the variant GRGESP peptide. Furthermore, a dodecapeptide corresponding to fibrinogen gamma 400-411 eluted only GPIIb-IIIa but not P160 from the RGD affinity matrix. Characterization of P160 by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by the O'Farrell gel electrophoresis system indicated that P160 is a component of platelet GPIc. GoH3, a monoclonal antibody recognizing the alpha subunit of the very late antigen-6, failed to immunoprecipitate P160 from the RGD eluate, indicating that it did not contain the very late antigen-6 alpha subunit. In immunoblots, P160 reacted specifically with a polyclonal anti-peptide antibody recognizing the alpha subunit of the vitronectin receptor (VnR), but not with the monoclonal anti-GPIIb antibody PMI-1, suggesting that P160 is the alpha subunit of platelet VnR. This possibility was further substantiated by the complete identity between the determined amino-terminal sequence of P160 and the known sequence of the VnR alpha subunit. Moreover, direct association of P160 with a beta subunit having an apparent molecular weight similar to that of GPIIIa was demonstrated by immunoprecipitation with LM609, an anti-VnR complex monoclonal antibody. These results indicate that the VnR complex is present on platelets and may play a functional role in platelet adhesive reactions.