Biochimica et biophysica acta最新文献

Under incubation conditions including deprivation of nitrogen sources, deprivation of lysine, inhibition by oxamycin and inhibition by penicillin, the accumulation of UDP-N-acetylamino sugar derivatives in Staphylococcus aureus cells, with time, has been studied. UDP-N-acetylglucosamine and UDP-N-acetylglucosamine-3-O-lactic ether accumulated in cells which were incubated in amino acid-free medium. During the initial phase of incubation there was a rapid rise in the appearance of UDP-N-acetylglucosamine followed later by a decrease of this nucleotide; concomitant accumulation of UDP-N-acetylglucosamine-3-O-lactic ether and UDP-N-acetylglucosamine-3-O-lactyl-peptides was observed under every condition which induced UDP-N-acetylglycosamine-3-O-lactyl-peptide accumulation. The relationship of the observed accumulation to the pathway of cell-wall mucopeptide synthesis is discussed.

The quantitative analysis of the carbohydrate components of ovine luteinizing hormone demonstrated the presence of 8 residues of N-acetylglucosamine, 3 residues of N-acetylgalactosamine, 7 residues of mannose, 2 residues of galactose, 1 residue of fucose and 0–1 residue of sialic acid per molecule. The number of residues of each carbohydrate subunit was calculated assuming a molecular weight of 28 000.

Collagen fibres have been allowed to form by warming soluble collagen at pH 7.4 to 37° in the presence of amounts of ascorbic acid which are within the physiological range (up to 10⁻⁴ M). Such fibres are more resistant to dispersion by denaturants, enzymes with little or no group specificity, and ultrasonic treatment than fibres formed in the presence of buffer alone. This stabilising effect appears to be associated with the enol grouping of ascorbic acid. The possibility of an analogous stabilisation mechanism in vivo is discussed.

• 1.

  1. The infrared spectra of partially purified acid mucopolysaccharide preparations from epiphyseal plate showed bands characteristic of chondroitinsulphate C as well as A, though no sharp chromatographic separation of the two was obtained.

• 2.

  2. Chromatography of unfractionated epiphyseal-plate extracts showed the presence of two protein peaks whose position in the elution pattern roughly coincided with two chondroitinsulphate peaks.

• 3.

  3. The rates of metabolism of the mixed chondroitinsulphates of various tissue extracts have been compared by the use of radioactive sulphate. The epiphyseal-plate chondroitinsulphate was metabolished at a much faster rate than from ribs. The chondroitinsulphate extractable only with alkali was distinguished from that extractable with water by a lower rate of metabolism, particularly evident in the extract of the epiphyseal-metaphyseal junction, and by the infrared spectrum, which indicates that it has a lower content of chondroitinsulphate C.

• 4.

  4. Chromatography of aqueous epiphyseal-plate extracts obtained at various times after injection of Na₂³⁵SO₄ demonstrated the depolymerisation in vivo of chondroitinsulphate, mainly prior to desulphation.

Mucopolysaccharides were obtained and fractionated from the skin of two eleasmobranch fishes, the Blue shark and Sandbar shark. In both species, the main polysaccharide fractions were hyaluronic acid, and chondroitin sulfate B. The total mucopolysaccharide content, however, varied considerably. In both species, the chondroitin sulfate B fractions were oversulfated. In both species, keratosulfate appeared to be present in small amounts.

A study of the diffusion behaviour of albumin, α-crystallin, fribrinogen, and turnip yellow mosaic virus in hyaluronic acid media has shown that the diffusion rates of these substances are markedly decreased by the presence of the polysaccharide. The relative decrease in the same as the corresponding effect observed on the sedimentation rates of these substances.

Investigation of eleven globular particles with diameters of 47–3650 Å established that the relative decrease of the sedimentation rate of a particle in the presence of hyaluronic acid was essentially a function of the diameter of the particle and the concentration of the polysaccharide and that the effect could be expressed by a simple exponential relationship. The results observed have been interpreted as a macromolecular-sieving effect of the polysaccharide.