Crystallization and properties of L-asparaginase fromEscherichia coli

Zusammenfassung L-Asparaginase ausE. coli ist bei hoher Proteinkonzentration zwischen pH 5,0 und 6,5 und geringer Ionenstärke durch Zugabe von Äthanol in der Kälte leicht kristallisierbar. Bei pH 5,0 und pH 6,5 entstehen unterschiedliche Kristallformen. Das durch Kristallisation gereinigte Enzym lässt sich bei erhöhter Temperatur inaktivieren, wobei das Produkt der Inaktivierung ebenso kristallisiert werden kann. Es zeigt das gleiche Verhalten in der Ultrazentrifuge wie das aktive Enzym.     

The surface glycopeptidolipids of mycobacteria: structures and biological properties

One of the most important opportunistic pathogens associated with acquired immunodeficiency syndrome (AIDS) is the M. avium complex. M. avium infections are found in up to 70% of individuals in advanced stages of AIDS. It is apparent that M. avium can replicate in host macrophages and persist for long periods. This group of mycobacteria are distinguished by the presence of unique, highly antigenic, surface-located lipids known as the glycopeptidolipids (GPLs). The GPLs are the chemical basis of the 31 distinct serovars of the M. avium complex, and have also been identified in some other species. The M. avium lipids are immunosuppressive and can induce a variety of cytokines that affect general host responses. Despite extensive chemical characterization of the structures of these GPLs, much work is needed to elucidate the molecular mechanism involved in this complex glycosylation pathway and its genetic basis. The challenges for the future lie in explaining the roles of these copious products in the intracellular life and infectivity of mycobacteria. The intention of our review is to offer a concise account of the structures of the M. avium lipids, their putative roles in the host responses, bacterial physiology and pathogenesis, particularly in immunocompromised patients such as those infected with human immunodeficiency virus (HIV). Advances in chemical synthesis of the various haptenic oligosaccharides are also given to demonstrate how these have helped to define the immunogenic determinants. We believe that future research should involve the creation of conditional mutants defective in these lipids for both functional and biosynthesis studies which will complement biological assays using chemically defined or modified neoglycoconjugates. Received 7 May 2001; received after revision 28 June 2001; accepted 28 June 2001     

Biochemical and immunological comparison of phenotypes of horse serum tranferrins

Résumé Différents phénotypes homozygotes des transferrines du sérum équin ont été comparés par analyses de leurs caractéristiques biochimiques et immunologiques. Les compositions en acides aminés des différents phénotypes sont très voisines; les différences immunologiques déterminées par la micro-fixation du complément sont plus prononcées.     

New antibiotics,trichopolyns A and B: Isolation and biological activity

Summary Polypeptide antibiotics, trichopolyns A and B, were isolated from the culture broth ofTrichoderma polysporum (Link ex Pers) Rifai (TMI 60146). Assessment of biological activity of the antibiotics against microorganisms was made.Acknowledgment. We are most grateful to Central Research Division, Takeda Chemical Industry Co. Limited, for determination of antifungal and antibacterial spectra.     

Chemical reactivity and biological properties of a series of aminochlorambucil derivatives]

The substitution of aminochlorambucil by a methyl group increased the chemical reactivity in IV b (n = 1) and IV b (n = 2) but their cytotoxicity remained low. The immunosuppressive effect (adjuvant arthritis in Rats and tuberculin related skin reaction) was observed with IV b (n = 2). Aminochlorambucil was effective on adjuvant arthritis only and IV b (n = 1) had no activity. Aminochlorambucil, IV b (n = 1) and IV b (n = 2) were devoid of any non-specific anti-inflammatory activity.     

Biochemical polymorphism of Japanese quail (Coturnix coturnix japonica): comparison of functionally different proteins (author's transl)]

The polymorphism observed among the enzymes involved in the respiratory metabolism (lactate dehydrogenase, malate dehydrogenase, phosphoglucomutase, phosphohexoseisomerase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase fructose 1-6 diphosphate dehydrogenase) is less important than that of the enzymes physiologically less essential, such as the various esterases, the alkaline phosphatase, the alcohol dehydrogenase, and of the non-enzymatic proteins (ovalbumin, ovoglobulins, ovomucoid, conalbumin, transferrin, etc.).     

Rheological properties of human blood plasma — A comparison of measurements with three different viscometers

Summary Human plasma viscosity was measured in capillary tube, cone-plate and Couette viscometers. The measurement of the viscosity at very low shear rates showed that plasma is a non-Newtonian fluid with a pseudoplastic rheological behaviour. The importance of this phenomenon for the microcirculation is discussed.We are grateful to OM Laboratories, Geneva, for providing the Contraves Low Shear 30 viscometer.     

Genome and cell sizes in frogs: A comparison with salamanders

Summary The nuclear volume (Nv), cell volume (Cv) and cell surface area (Cs) of erythrocytes from 26 anuran species show a linear and direct correlation with the nuclear DNA content; the Cs/Cv ratio tends to decrease as DNA increases. Analogous phenomena are found in urodeles possessing less than 70 pg/N of DNA, whereas in those with a larger genome there is a trend towards stabilization of the Cs/Cv ratio. The same mechanisms appear to control the ratios of genome sizes to cell sizes within the amphibians and possibly in other vertebrates as well. The former, however, seem to avail themselves to a greater extent of the adaptive properties inherent in their genome and cell size variations.Research supported by a grant from the Italian CNR.     

Preparation and biological properties of (-)- and (+)-6-hydroxydopa

Zusammenfassung Die optischen Isomeren von 6-Hydroxydopa wurden synthetisiert und ihr Effekt auf den Katecholaminspiegel verschiedener Organe in der Ratte bestimmt. Dem (–)-Isomeren gegenüber waren Herz und Nebennieren äusserst empfindlich und im Gehirn wurde der Norepinephrinspiegel erniedrigt.

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B.A.B. is the recipient of a Roche Institute of Molecular Biology postdoctoral fellowship.