摘要:

AbstractThe function of blood is to deliver nourishments to and remove wastes from all parts of the body. It is made up of different kinds of cells bathed in a fluid called plasma. The major cellular components of blood include (1) red blood cells for carrying oxygen to the various tissues, (2) white blood cells for providing defense against infectious agents and cancer, and (3) platelets for inducing a cascade of events leading to blood clot formation that stops bleeding. The plasma also contains numerous proteins for maintaining normal balance in our body, and include (1) clotting factors such as factor VIII, factor IX, fibrinogen, and thrombin, (2) protease inhibitors and anticoagulants that regulate the coagulation pathway, the complement system, or the fibrinolytic system, (3) immunoglobulin which are antibodies directed against different infectious agents, and (4) albumin which functions as a volume expander to maintain our blood volume and is essential when threatened with severe blood loss.The plasma of the invertebrate horseshoe crab, contains three major proteins: hemocyanin, C‐reactive protein (CRP), and α2‐macroglobulin. Hemocyanin functions as an oxygen‐carrying protein. CRP is a lectin that binds to phosphocholine of the pneumococcus C‐polysaccharide, to the chromatins of damaged cells, and to the galactose moiety of desialylated glycoprotein as a membrane‐associated protein on liver marcrophages. CRP exists, however, as a normal component of the invertebrate hemolymph. α2‐macroglobulin exhibits proteinase inhibitory activity with a broad specificity that can block the activities of protease secreted from invading microorganisms. The Limulus CRP, along with the C3 homologue α2‐macroglobulin, participates in a complement ‐ like hemolytic activity in horseshoe crab hemolymph.Whereas the vertebrate evolved to use both the innate and the adaptive immunity, the invertebrate only uses the innate immunity. The innate immunity uses germ‐line encoded receptors to recognize conserved molecular constituents of infectious microorganisms, is phylogenetically older, with some of its form presumably presents in all multicellular organisms. The adaptive immunity is mediated by highly specific antigen receptors that are distributed clonally on the two types of lymphocytes, the T‐cells and the B‐cells. Evidence has accumulated in recent years to suggest that the innate immune system provides signals that are essential for the adaptive immune response to generate information on the origin of the antigen and the type of response to be induced. This linkage invites renewed interest in the study of the innate immune syst

ISSN:0009-4536    

DOI:10.1002/jccs.199900042

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY

摘要:

AbstractCarbohydrates have been known as poor candidates for drug development. Recent studies have, however, shown that structurally simplified small molecules as mimics of complex carbohydrates recognized by receptors can be developed as inhibitors of carbohydrate‐mediated biological recognition. In addition, small molecules with higher affinity and specificity than the parent ligands can be developed by incorporating additional hydrophobic or charged groups in the carbohydrate mimetic which contains essential functional groups for receptor binding. Representative examples are illustrated in the studies of sialyl Lewis x ‐ selectin interactions, glycosidase and glycosyltransferase reactions and aminoglycoside antibiotic ‐ RNA interac

ISSN:0009-4536    

DOI:10.1002/jccs.199900043

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY

摘要:

AbstractOne of the diversities of carbohydrate structure lies in their ability to form different anomers from the monosaccharide unit. Unfortunately, the question of assignment of anomers has not been dealt with properly or accurately in most organic and biochemical textbooks and reference books. In this article, the question of assignment of anomers is examined from several different standpoints and an easy solution for this tricky problem is suggested.

ISSN:0009-4536    

DOI:10.1002/jccs.199900044

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY

摘要:

AbstractInternal electron transfer in bovine cytochromecoxidase was initiated by CO photolysis of the CO‐bound mixed‐valence form of the enzyme. Transient absorption spectroscopy was used to monitor changes in the redox states of the metal centers in the enzyme brought about by electron re‐equilibration. Upon CO photodissociation, reduced high spin cytochromea3was generated in less than 0.1 μsec, and a portion of the reduced cytochromea3was reoxidized with biphasic rate constants of k1= 1.0 × 106s−1and k2= 7.8 × 104s−1. Concomitant reduction of cytochromeawas also observed with biphasic rate constants of k1= 1.6 × 106s−1and k2= 9 × 104s−1. The stoichiometry of cytochromea3oxidized to cytochromeareduced was found to be close to 1:1. Contrary to similar studies in the literature, no reduction of CuAwas observed. As a control, no transient absorption changes corresponding to electron transfer was observed in the CO‐inhibited fully reduced form of the enzyme. These results indicate that there is significant electron reequilibrationonlybetween cytochromea3and cytochromeaupon photolysis of the CO‐boun

ISSN:0009-4536    

DOI:10.1002/jccs.199900045

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY

摘要:

AbstractThe industrial alkaline protease, alcalase, is stable and active in a high concentration of organic solvents and useful as a biocatalyst for (i) diastereoselective hydrolysis of peptide esters and preparation of racemization‐free peptides; (ii) selective incorporation of esters of D‐amino acid into peptides in t‐butanol via a selective hydrolysis of esters of D,L‐amino acid, followed by using the unhydrolyzed D‐esters as a nucleophile in a kinetically controlled peptide bond formation; (iii) resolution of esters of amino acid in 95% t‐butanol/5% water, followed by saponification of the unreacted esters to offer both enantiomers with high yield and optical purity; (iv) completely resolve amino‐acid esters with high yield and optical purity viain situracemization of the unreacted antipode catalyzed by pyridoxal 5‐phosphate; (v) cryobioorganic synthesis of peptides with increased yields 15%–40% of peptide bond formation by reaction at 5 °C instead of 25–30 °C of a kinetically controlled enzymatic

ISSN:0009-4536    

DOI:10.1002/jccs.199900046

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY

摘要:

AbstractMonofunctional, bifunctional and trifunctional poly‐2′‐(2,4‐dinitrophenyl)‐oligoribonucleotides have been designed and synthesized as inhibitors of retroviruses. These compounds are membrane‐permeable, ribonuclease‐resistant, and apparently mutation‐insensitive inhibitors of reverse transcriptases. These inhibitors have been tested for the treatment of murine leukemia as an animal model related to AIDS. Although the monofunctional inhibitor is already 100% effective for the treatment of murine leukemia, its efficacy can be increased by two orders of magnitude by introducing antisense sequences in the nucleotide backbone so that the resulting multifunctional inhibitor can also disrupt the synthesis of specific viral proteins. The entropy advantage of multifunctionality in the design of antiviral agen

ISSN:0009-4536    

DOI:10.1002/jccs.199900047

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY

摘要:

AbstractA review of research on snake neurotoxin is presented, with emphasis on the chemical modification studies and molecular cloning of postsynaptic and presynaptic neurotoxins fromNaja naja atra(Taiwan cobra) (Fig. 1a) andBungarus multicinctus(Taiwan banded krait) (Fig. 1b). Cobrotoxin and α‐bungarotoxin are the primary postsynaptic neurotoxins isolated from the venom ofN. naja atraandB. multicinctus, respectively. Although they share a common three‐dimensional structure, the functional elements essential for the manifestation of their toxicity are different. Selective and stepwise chemical modification of cobrotoxin indicate that at least two cationic groups, an ϵ‐amino group of Lys‐47 and a guanidino group of Arg‐33 common to all known postsynaptic neurotoxins, are functionally important for its neuromuscular blocking activity. However, for α‐bungarotoxin, the side chains of several basic amino acid residues are involved in the multipoint contact between the toxin and acetylcholine receptor. Moreover, the conserved Trp residue is essential for the neurotoxicity of cobrotoxin, but not for α‐bungarotoxin. The cDNAs encoding cobrotoxin and α‐bungarotoxin was constructed from the cellular RNA isolated from the venom glands ofN. naja atraandB. multicinctusby polymerase chain reaction. The sequence of their 3′‐untranslational region, signal peptide and 5′‐untranslational region share a high degree of homology, suggesting that they are evolutionarily related. Expression of both neurotoxic protein inE. coligenerated polypeptide chains for reactions with the antisera against the native neurotoxins.Presynaptic neurotoxins constitute a different group of neurotoxic proteins in snake venom proteins. These presynaptic neurotoxins are either basic phospholipase A2(PLA2)per seor contain basic PLA2as an indispensible part of their structures. Thus, the presynaptic neurotoxins usually show both PLA2activity and presynaptic neurotoxicity. β‐Bungarotoxin (β‐Bgt), the main presynaptic PLA2neurotoxin isolated from the venom ofB. multicinctus(Taiwan banded krait), consists of two dissimilar polypeptide chains, a PLA2subunit (A chain) and potassium channel recognition subunit (B chain). Chemical modification studies show that the toxin might possess two functional sites, one responsible for the catalytic activity and the other for its pharmacological properties. Molecular cloning and expression of the A chain and B chain of β‐Bgt reveal that the A chain of β‐Bgt is an active subunit with PLA2activity, and that the B chain is involved in voltage‐gated potassium c

ISSN:0009-4536    

DOI:10.1002/jccs.199900048

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY

摘要:

AbstractLinear orbital vibronic constants are calculated within the Extended Hückel formalism and used to evaluate the forces acting on the atoms along the symmetry coordinates, in a planar arrangement of four identical atoms. It is shown, from the magnitude and direction of the forces, that the high‐symmetry square planar arrangement is unstable and distorts to lower symmet

ISSN:0009-4536    

DOI:10.1002/jccs.199900049

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY

摘要:

AbstractTwo oxoruthenium(IV) complexes containing C2symmetric 1,1′‐biisoquinoline (biqn) and (R,R)‐3,3′‐(1,2‐dimethylethylenedioxy)‐2,2′‐bipyridine (diopy*) were prepared, and both are active oxidants for alkene epoxidations. The oxidation of styrene andcis‐ andtrans‐β‐methylstyrenes by [(Cn)(diopy*)‐RuIV(O)](ClO4)2did not proceed enantioselectively, but the same oxidant can attain a moderate enantioselectivity of 33%ee for thetrans‐stilbene oxidation totrans‐stilbene oxide. A head‐on approach model, where the C=C is directed from the top to the O=Ru moiety, is proposed to account for the facial differentiatio

ISSN:0009-4536    

DOI:10.1002/jccs.199900050

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY

摘要:

AbstractAdvances in sensitive optical measurement schemes have led to the detection and the physical and chemical characterization of single biological cells and individual molecules. These technological achievements are much more than the ultimate milestone in low‐level monitoring. Potential applications include DNA sequencing at high speeds, probing microscale environments, monitoring environmental pollution, studying the variability of molecular conformations, detecting disease infection at an early stage, and devising molecular‐scale imaging pro

ISSN:0009-4536    

DOI:10.1002/jccs.199900051

出版商:WILEY‐VCH Verlag    

年代:1999

数据来源: WILEY