Selective monitoring of peptidase activities with synthetic polypeptide substrates and polyion-sensitive membrane electrode detection

A novel method to monitor specific peptidase activities in biological samples as complex as undiluted plasma/blood is described. The approach is based on the design of synthetic polypeptide substrates in which di- or triarginine sequences are linked to each other via one or more other amino acids recognized specifically by the peptidase to be determined. Detection of chymotrypsin and renin activities using synthetic substrates P4 (F-R-R-R-F-V-R-R-F-NH2) and P5 (R-R-R-L-L-R-R-L-L-R-R-R), respectively, serves to demonstrate the principles of this new assay system. A polyion-sensitive membrane electrode, prepared by doping polymer films with dinonylnaphthalene-sulfonate (DNNS), is shown to exhibit significant nonequilibrium electromotive force (EMF) responses toward these and other polycationic substrates at microgram/milliliter levels under physiological conditions. The same electrode, however, exhibits much smaller total EMF response toward the shorter fragments of the synthetic peptides generated by peptidase activity; hence, the addition of peptidase to a solution containing the synthetic substrate yields a change in electrode EMF response, the rate of which is proportional to the activity of peptidase present. Other synthetic polycationic peptides as well as natural polycationic peptides (e.g., protamine) that lack specific cleavage sites for chymotrypsin and renin, yet are detected by the DNNS-based membrane electrode, do not elicit any significant change in EMF response in the presence of the peptidases, confirming the feasibility and utility of the proposed bioanalytical method.     

Polymorphism of bacteriophage T7

For viruses made of nucleic acid and protein, the structure of the protein outer shell has, in the past, been found to be uniquely determined by the viral genome. However, here, non-denaturing agarose gel electrophoresis of bacteriophage T7 reveals two states of the mature T7 capsid; the conditions of growth are found to alter the population by T7 of these two electrophoretically defined states. Both states have been previously observed for a genetically altered T7 and they are observed here for wild-type T7. The average electrical surface charge density of a bacteriophage particle (delta) determines its state; the delta of particles in both states is negative. For a given condition of growth, the population of these two states is influenced by the extent to which the major T7 outer shell protein, p10A, is accompanied by its minor readthrough variant, p10B. Comparison of the two electrophoretic states reveals the following. (1) No difference in radius is present in the outer shell (+/-2%). (2) As the pH of electrophoresis is either increased or decreased from neutrality, the state becomes more highly populated for which delta is greater in magnitude (state 1). By changing the pH, some T7 particles are made to change state. (3) Particles in state 1 adsorb less quickly to host cells than do the particles in the alternative state (state 2). This latter observation suggests the hypothesis that state 1 evolved to reduce the probability of re-initiating an infection when conditions are not favorable for growth. This hypothesis is supported by the observation that, as conditions of growth become apparently more unfavorable, progeny increasingly populate state 1.     

Comment on new differential flip-flops from Yuan and Svensson

A family of differential latches has recently been proposed by Yuan and Svensson [1996]. The author shows that the proposed flip-flops using the dynamic slave latch suffer from a poor logic-level zero in the presence of glitches on the data inputs     

Histogram measurement of ADC nonlinearities using sine waves

This paper gives results concerning the measurement of differential and integral nonlinearity of ADC's using the histogram method with a sine wave input signal. We specify the amount of overdrive required as a function of the noise level and the desired accuracy and the number of samples required as a function of the desired accuracy, the desired confidence level, and the noise level. An analysis of the effect on the results of harmonic distortion of the applied signal is given. The error analysis assumes a mixture of coherent and random sampling rather than pure random sampling     

Human gamma-interferon expression in the mammary gland of transgenic mice

Transgenic mice carrying a hybrid gene consisting of ovine beta-lactoglobulin gene sequences and human gamma-interferon (hIFN-g) cDNA were produced. hIFN-g expression in the mammary gland of two lactating transgenic founder females was found. The concentration of active hIFN-g in the milk was estimated as being ca. 1800 IU/ml. The hIFN-g ability to express in the mammary gland was found in the progeny of transgenic founder male.     

Anthroposophic perspectives in primary care

Anthroposophically Extended Medicine (AEM) is a truly integrative healing system. AEM represents an expansion, not an alternative to conventional medicine. Its unique understanding of the interplay among physiological, soul and spiritual processes in healing and illness serves to bridge allopathy with naturopathy, homeopathy, functional/nutritional medicine and other healing systems.     

Variants of chromosome 9 in phenotypically normal individuals

The human chromosome 9 displays the highest degree of structural variability. Four different types of variants are described including pericentric inversion, extra G-positive band in the q arm, additional G-positive band in the p arm and duplication of band 9q21-q22. It is important to demonstrate inheritance from a phenotypically normal individual in order to differentiate between a variant chromosome and an abnormal chromosome.