Extraction and solubility characteristics of zein proteins from dry-milled corn.

Zein isolation by aqueous ethanol extraction from dry-milled corn produces a mixture of zeins, covalently linked polymers (dimers, tetramers, etc.) and higher-molecular-weight aggregates, some of which were not soluble in aqueous alcohol. The insoluble particles were identified as protein aggregates which form when the extraction solution is heated, particularly under alkaline conditions. The insoluble protein aggregates were not present in zein isolated by the same method from corn gluten meal. Zeins extracted from corn gluten meal and dry-milled corn were fractionated (by differential solubility) to identify differences in their polypeptide compositions. Using polyacrylamide gel electrophoresis, beta- and gamma-zeins were detected in dry-milled corn, but only trace amounts of beta-zein were found in corn gluten meal. Treatment of dry-milled corn with 0.55% lactic acid and 0.2% sulfur dioxide at 50 degrees C for 6 h before ethanol extraction resulted in a 50% increase in zein isolate yield with high solubility (98%). This pre-extraction treatment cleaved disulfide linkages of the beta- and gamma-zeins and significantly reduced insoluble aggregates in zein isolates.

Enzymatic hydrolysis, grease permeation, and water barrier properties of zein isolate coated paper.

An inexpensive zein-lipid mixture was isolated from yellow dent, dry-milled corn. Grease permeation through zein isolate applied to brown Kraft paper was found to be independent of loading levels at zein isolate levels above 30 mg/16 in.(2). The data shows that water vapor transmission rates depended on the amount of coating applied. Triacylglycerols were the most abundant lipid in milled corn but were absent in the zein isolate (perhaps due to hydrolysis by lipases). Zein from the paper was hydrolyzed enzymatically and the hydrolysis monitored by SDS-capillary electrophoresis. At an E:S ratio of 1:100 no further increase in the hydrolysate peak occurred after 10 and 30 min for alpha-chymotrypsin and pancreatin 8 x; however, zein and lipid were still present 1 h after hydrolysis by pancreatin 1 x.

Preparation, isolation, and characterization of cutin monomers and oligomers from tomato peels.

Cutin in tomato peels was depolymerized in methanolic base to yield cutin monomers or a mixture of cutin oligomers. These products were isolated by typical solvent extraction methods or by precipitation, and the isolates were characterized by chromatographic and spectroscopic analyses. It was determined that the compositions of the isolates from both isolation procedures were similar, although solvent extraction gave higher yields. However, the precipitation method, which is easy to carry out and avoids the use of undesirable organic solvents, may be preferable in commercial processes for recovering these compounds.

Reducing occupational exposure to blood in the OR.

1. Many occupational exposures to blood in the operating room can be prevented. Some percutaneous injuries may not be preventable, but their frequency can be reduced by implementing engineering and work practice controls. Work practice controls and personal protective equipment can help eliminate mucocutaneous exposures to blood. 2. Identifying risk factors for intraoperative exposure is a vital step in presurgical and intraoperative assessment to plan infection prevention and control interventions. The decision to use risk reduction strategies should be based on probability and type of exposure anticipated rather than on the index of suspicion for bloodborne infection in the patient. 3. The responsibility for using safety and barrier precautions in the operating room remains that of the health-care worker. Not only the patient, but also the health-care worker need to be protected.

Phosphorylation of beta-casein and alpha-lactalbumin by casein kinase from lactating bovine mammary gland.

Two milk proteins, beta-casein and alpha-lactalbumin, were compared as substrates for casein kinase from bovine mammary gland. beta-Casein could be rephosphorylated after removal of its phosphate groups, whereas alpha-lactalbumin was an effective substrate after the protein had been reduced and carboxymethylated. The native proteins could not be phosphorylated. Magnesium2+, Ca2+, and Mn2+ stimulated phosphorylation of the modified proteins. Calcium2+ was the most effective cation for alpha-lactalbumin and Mn2+ for beta-casein. Michaelis constants were 144 microM for alpha-lactalbumin in the presence of Ca2+ and 142 microM for beta-casein in the presence of Mn2+; however, the maximum velocity for alpha-lactalbumin was three times that of beta-casein. After phosphorylation with [gamma-32P] ATP, partial hydrolysis showed that only serine residues were phosphorylated in both proteins. Chymotryptic peptides of phosphorylated alpha-lactalbumin and tryptic peptides of phosphorylated beta-casein were examined by HPLC and selected peptides were analyzed for amino acid content. Comparison of the analyses with sequence data showed that serine at position 47 in alpha-lactalbumin is the major site of phosphate incorporation. Dephosphorylated beta-casein was only partially rephosphorylated. However, the sites identified correspond to the phosphorylated residues in native beta-casein, namely, serine at position 35 and the cluster of four serines between residues 15 and 20.

Occupational risk of HIV, HBV and HSV-2 infections in health care personnel caring for AIDS patients.

We have prospectively followed for 9-12 months, 246 female health care workers (HCWs): 102 with high exposure (HE), 43 with low exposure (LE), and 101 with no exposure (NE) to AIDS (acquired immunodeficiency syndrome) patients. No HCWs have clinical, serologic, or immunologic evidence of HIV (human immunodeficiency virus) infection. No HCWs in the HE group seroconverted to cytomegalovirus (CMV). One HCW in the HE group seroconverted to Hepatitis B virus (HBV), another HCW in the HE group seroconverted to herpes simplex virus type 2 (HSV-2) although all three groups were similar with respect to HBV and HSV-2 seropositivity. If hospital infection control practices are employed when HCWs care for AIDS patients or work with their biological specimens, the risk of occupationally acquiring a HIV, CMV, HBV or HSV-2 infection appears to be low.

Influence of pH on organic acid production by Clostridium sporogenes in test tube and fermentor cultures.

The influence of pH on the growth parameters of and the organic acids produced by Clostridium sporogenes 3121 cultured in test tubes and fermentors at 35 degrees C was examined. Specific growth rates in the fermentor maintained at a constant pH ranged from 0.20 h-1 at pH 5.00 to 0.86 h-1 at pH 6.50. Acetic acid was the primary organic acid in supernatants of 24-h cultures; total organic acid levels were 2.0 to 22.0 mumol/ml. Supernatants from pH 5.00 and 5.50 cultures had total organic acid levels less than one-third of those found at pH 6.00 to 7.00. The specific growth rates of the test tube cultures ranged from 0.51 h-1 at pH 5.00 to 0.95 h-1 at pH 6.50. The pH of the medium did not affect the average total organic acid content (51.5 mumol/ml) but did affect the distribution of the organic acids, which included formic, acetic, propionic, butyric, 3-(p-hydroxyphenyl)propionic, and 3-phenylpropionic acids. Butyric acid levels were lower, but formic and propionic acid levels were higher, at pH 5.00 than at other pHs.

Liquid chromatographic separation of bile acids.

The recent revival in interest in the role of bile acids in biological systems has emphasised the importance of analysing individual bile acids for the presence of closely related impurities. An assessment of the value of modern, high-performance liquid chromatography for this application has shown that mixtures of underivatised bile acids may be resolved by reversed-phase chromatography. Separation of isomeric acids and those differing in the extent of hydroxyl substitution is possible by this approach. Mixtures of amino acid conjugates of bile acids may also be resolved by this method. The use of an ultraviolet absorbance detector, operating at a wavelength in the region of 210 nm, results in a detection limit in the order of 50 ng.