Enzymatic O-glycosylation of kappa-caseinomacropeptide by ovine mammary Golgi membranes

The results of subcellular fractionation of sheep mammary gland membranes indicate that N-acetylgalactosaminyl polypeptide transferase and galactosyl-N-acetylgalactosaminyl transferase, which are involved in the assembly of disaccharide units of kappa-casein, are localized chiefly in Golgi membranes. The glycosyltransferase activities incorporating N-acetyl [1-14C] galactosamine and [U-14C] galactose from uridine diphosphate N-acetyl [1-14C] galactosamine and uridine diphosphate [U-14C] galactose, respectively, were measured after membrane solubilization with Triton X-100 either with unglycosylated caseinomacropeptide, or with this polypeptide containing the N-acetylgalactosamine side chain residues (desialylated and degalactosylated caseinomacropeptide). Radioactive N-acetylgalactosamine was incorporated in the unglycosylated acceptor peptide, and the glycosidic bonds in the product were alkali labile, suggesting that they were linked to the hydroxyamino acid residues. In addition radioactive N-acetylgalactosamine was released after alpha N-acetyl-D-galactosaminidase treatment of labelled caseinomacropeptide. [U-14C] galactose was incorporated in the desialylated and degalactosylated acceptor peptide. Reductive alkaline treatment of [U-14C] galactose peptide resulted in the release of a major product, the chromatographic properties of which in TLC were identical with authentic galactosyl (1 leads to 3) N-acetylgalactosaminitol. The structure of the labelled disacchariditol determined after periodate oxidation (two equivalents) by gas liquid chromatography-mass spectrometry revealed that the [U-14C] galactose was linked to position C-3 on the N-acetylgalactosaminyl-residue. The anomery of the galactose, as determined by a chemical method, indicates unambiguously a beta configuration.     

Uncoupling of mitochondrial oxidative phosphorylation by thallium.

The mechanism of integration of λ$\text{bio}$ll, which is deleted of all the known λ recombination genes, was studied using $\text{bio}$ deleted hosts as recipients. The presence of $\text{rec}$BC DNase and $\text{exo}$I in the recipient cells affected the fate of λ$\text{bio}$ll DNA. In nine of ten $\text{imm}\text{λ}{}^{\mathrm{+}}$ transductants, insertion of the λ$\text{bio}$ll genome took place somewhere between J and N and the remaining one had abnormally permuted prophage λ. In this lysogen (#42), the sequence of prophage genes was similar to that of vegetative phage λ. The properties of lysogen #42 were compared with those of other lysogens.     

Fluorescence anisotropy from diphenylhexatriene in rat liver plasma membranes

Rat livers were fractionated to obtain intracellular membrane preparations and a highly purified preparation of bile canaliculi. The fraction containing bile canaliculi was homogenized and subfractionated to give fractions representing fragments of contiguous membrane and of canalicular microvilli. The relative purity and extent of contamination of each preparation was determined. When the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene was incorporated into aliquots of each fraction at the same probe: lipid ratio and the steady-state anisotropy of its fluorescence measured, it was found that the plasma membrane preparations were much more ordered than the intracellular membrane preparations. Of the plasma membrane preparations, that containing the canalicular microvilli was the most ordered, even allowing for any contribution of contaminants. Thus the microvillus membrane of the bile canaliculus appears to be the most ordered domain of the plasma membrane of the hepatocyte. The high order in this domain may be a factor in reducing the susceptibility to bile salt damage during bile secretion, since it is this region which is exposed to high concentrations of bile salts in vivo.     

Cellulose-microfibril-orienting mechanisms in plant cells walls

A brief review is given of the changing views over the years, as knowledge of wall structure has developed, concerning the mechanism whereby cellulose chains may be oriented. This leads to an examination of current concepts, particularly those concerning microtubules. It is shown that none of the mechanisms suggested whereby microtubules might cause orientation of cellulose microfibrils is consistent with the known range of molecular architectures found in plant cell walls. It is further concluded that any mechanism which necessitates an indissoluble link between the plasmalemma and the cellulose-synthesising complex at the tip of a microfibril is unacceptable. A new proposal is presented in which it is speculated that both microtubules and microfibrils are oriented by a mechanism separate from both. It is shown that if two vectors are contemplated, one parallel to cell length and one at right angles, and a sensor exists on the plasmalemma surface which responds to changes in the vectors, then all known wall structures may be explained. The possible nature of the vectors and the sensor are considered.     

Restriction fragment length polymorphism (RFLP) analysis of bovine nuclear protein genes

Summary We have recently cloned both the bovine protamine (Krawetz et al. 1987, DNA 6: 47–57) and high mobility group (HMG-1) cDNAs (Pentecost and Dixon 1984, Bioscience Reports 4: 49–57). They have been used as probes for Restriction Fragment Length Polymorphism analysis of male-female pairs of different species and breeds, within the genus Bos. Utilizing this approach we have studied inheritance, chromosomal location and gene copy number of the bovine protamine and HMG-1 genes. This revealed that these nuclear protein genes are highly conserved suggesting that selective pressure has maintained their gene structures during evolution. A polymorphic Taq 1 restriction fragment was identified that was shown to be a heritable marker. These genes are not sex-linked and are present in a single copy for protamine and at least two copies for the HMG-1.     

Reaction mechanism of surfactant‐sensitized chemiluminescence of bis(2,4,6‐trichlorophyenyl) oxalate and hydrogen peroxide induced by gold nanoparticles

The chemiluminescence (CL) of bis(2,4,6‐trichlorophyenyl) oxalate with hydrogen peroxide in the present of cationic surfactant and gold nanoparticles was studied. The CL emission was obviously enhanced in the presence of surfactant at a suitable concentration, with a synergetic catalysis effect exhibited. Different sizes of gold nanoparticles (15 and 50 nm) showed different effects on CL intensity. Mechanisms of the CL reaction and sensitization effect are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Continuity and Creativity in Iroquois Beadwork

This review essay of Across Borders: Beadwork in Iroquois Life focuses on the display of beadwork as a cultural practice that has evolved significantly throughout its history while remaining central to Iroquois identity. The exhibition draws on historical documentation, objects, and imagery that depict the varied uses of beadwork as ritual objects, sources of income, markers of identity, and as works of art. The content and narrative for the display was developed through a broad collaboration between curators, scholars, artists, and members of two Iroquois communities. The changing and continued importance of beadwork is reflected in the adaptation of materials and styles for different forms of production and use. Across Borders places Iroquois beadwork in a broad context while concentrating on specific forms and meanings that are attached to beadwork, whether created in community gatherings or by individual artists.