A high-repetition-rate, fast temperature-programmed gas chromatograph and its online coupling to a supercritical fluid chromatograph (SFC × GC).

We present a fast gas chromatographic system that can be used as a second dimension in comprehensive two-dimensional (supercritical fluid × gas) chromatography (SFC × GC). The temperature of the short (1 m long) capillary column is controlled by a resistively heated coaxial stainless-steel tube. The electrical resistance and, therefore, temperature of the stainless-steel tube are measured by continuous monitoring of the current/voltage ratio. Highly repeatable heating rates of up to 2100 °C min-1 (35 °C s-1) are obtained, which should be high enough for the most demanding fast chromatograms. To reduce the cooling time between temperature programs, the column is cooled by injecting evaporating carbon dioxide into the space between the coaxial heater and the column. This gives cooling rates of 5100 °C min-1 (85 °C s-1), which allows quick succession of temperature programs. More repeatable heating profiles with stable GC retention times together with faster cooling are significant improvements on previous SFC × GC systems. Cycle times of four gas chromatograms per minute could readily be achieved, which allows efficient coupling to high-resolution stop-flow SFC in the first dimension. We demonstrate the fast chromatograph by separating fatty acid methyl esters, yielding information that would be useful in the food and biodiesel industries.

A systematic review of counselling for HIV testing of pregnant women.

BACKGROUND: Evidence-based strategies have made it possible to limit mother-to-child transmission of the HI-virus to a large extent and enable HIV-positive women to stay healthy for longer, provided their HIV status is known. Although voluntary counselling and testing for HIV is part of routine antenatal care in South Africa, the uptake of testing varies and a large number of pregnant women's HIV status is not known at the time of birth. AIM: The aim of the study was to establish research evidence regarding factors influencing counselling for HIV testing during pregnancy by means of systematic review, forming part of a larger study using a variety of evidence to develop best practice guidelines. DESIGN: Systematic review. METHODS: The question steering the review was: 'What factors influence counselling for HIV testing during pregnancy?'. A multi-stage search of relevant research studies was undertaken using a variety of sources. A total of 33 studies were retrieved and critically appraised. Data were extracted from the studies and assessed according to its applicability in the South African context. RESULTS: The results are presented according to the following themes: effects of counselling, quality of counselling, group vs. individual counselling, ways of offering HIV testing, rapid testing, counselling and testing during labour, couple counselling and testing, counsellor and organisational factors. CONCLUSIONS: According to research evidence, factors such as whether counselling is presented in a group or individually, different ways to present HIV testing as well as counsellor and organisational factors can influence counselling for HIV testing during pregnancy. When developing best practice guidelines for settings very dissimilar from where the research was done, research evidence must be contextualised. RELEVANCE TO CLINICAL PRACTICE: Implementation of the best practice guidelines may lead to the increased uptake of HIV testing in pregnancy in developing countries like South Africa and thus to an increase in the number of women whose status is known when their babies are born.

[Countercurrent distribution of polysulfonated proteins (author's transl)]. / Gegenstromverteilung von poly-sulfonierten Proteinen

The reaction of bovine beta-lactoglobulin AB with reagents 4-(isothiocyanato) benzene sulfonic acid, 5-(isothiocyanato) benzol-1,3-bis(sulfonic acid) and 7-(isothiocyanato) naphthalene-1,3,5-tris(sulfonic acid) is described. The blocking of the epsilon-amino groups of lysine is quantitative. The thus modified protein can be analysed in the countercurrent distribution apparatus and can be split very rapidly at the arginine residues with trypsin.

Naja melanoleuca (forest cobra) venom. Purification and some properties of phospholipases A.

Three phospholipases A (Fractions DE-I, DE-II and DE-III) were purified from Naja melanoleuca (Forest cobra) venom by a combination of gel filtration on Sephadex G-50 and chromatography on DEAE-cellulosemthe purified phospholipases A were homogeneous by various physicochemical criteria. Whereas Fraction DE-I contains 118 amino acid residues, Fractions DE-II and DE-III comprise 119 residues. The three enzymes are cross-linked by seven disulphide bridges, have asparagine as N-terminal amino acid and the C-terminal is glutamic acid or glutamine. The molecular weights of the three phospholipases A from sedimentation analysis at pH 2.1, also by the sodium dodecylsulphate-gel method and calculated from the amino acid composition, were close to 13 000. Studies of circular dichroism in the spectral region between 195 to 305 nm showed that the three phospholipases A contain similar helical contents but revealed conformational differences between their side-chain chromophores.