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1.
A new sulfur-containing imidazole compound, m.p. 218~223°C (decomp.), [α]D24+7.4° in water), C11H19N3O3S was isolated from sclerotia of Sclerotinia libertiana and named sclerothionine. The chemical structure of sclerothionine was identified with 2-hydroxyethyl-ergothioneine which was synthesized from ethylene chlorhydrine and ergothioneine.  相似文献   

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Some physicochemical properties and amino acid composition of alkaline proteinase from Aspergillus sojae were found to be as follows: The isoelectric point was at pH 5.1. The molecular weight was 25,500 using the Sheraga-Mandelkern’s formula, based upon the values of the sedimentation coefficient (s20,w°=?2.82?S), the intrinsic viscosity ([η] = 0.027 dl/g), and the partial specific volume (V¯?=?0.726?ml/g). The enzyme contains 16.8% of nitrogen and is composed of 250 residues of amino acid; Asp31 Glu19, Gly27, Ala32, Val18, Leu14, Ile14, Ser28, Thr18, (Cys C?ys)1, Met2, Pro6, Phe7, Tyr8, Trp2, His5, Lys14, Arg3, (amide-NH3)20.  相似文献   

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Sclerone, mp 138~140°C, C10H10O3 was isolated from the culture filtrate of Sclerotinia sclerotiorum. This is optically active, [α]D20?30°, and gave 1,5-naphthalenediol on pyrolysis. Oxidation with MnO2 yielded juglone. From the chemical and physical evidences, the structure was determined to be 4,5-dihydroxy-(4S)-3,4-dihydro-1(2H)-naphthalenone.  相似文献   

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Amylose-borate interaction has been analyzed by frontal gel chromatography, using the constituent velocity data alone. The constituent Velocity equation was reformulated in terms of elution volume for a type of interacting system described byA+iB=ABi(i=1,2,3n)

Detailed examination of the binding data indicates that, in the complex formation between amylose and borate, this type of equilibria operates predominantly, if not solely. Use of the constituent elution volume equation enabled us, for the first time, to evaluate the association constant (K) and number of binding site pertaining to this system, i.e., K = 4.9 102 and n = 1. There was no evidence indicating the occurrence of the formation of inclusion complex.  相似文献   

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In this paper, we develop a new technique to study the treewidth of graphs with bounded degree. We show that the treewidth of a graph G = (V, E) with maximum vertex degree d is at most (1Ce4.06d)|V| for sufficiently large d, where C is a constant.  相似文献   

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Owing to their ability to break glycosidic bonds in recalcitrant crystalline polysaccharides such as cellulose, the catalysis effected by lytic polysaccharide monooxygenases (LPMOs) is of major interest. Kinetics of these reductant-dependent, monocopper enzymes is complicated by the insoluble nature of the cellulose substrate and parallel, enzyme-dependent, and enzyme-independent side reactions between the reductant and oxygen-containing cosubstrates. Here, we provide kinetic characterization of cellulose peroxygenase (oxidative cleavage of glycosidic bonds in cellulose) and reductant peroxidase (oxidation of the reductant) activities of the LPMO TrAA9A of the cellulose-degrading model fungus Trichoderma reesei. The catalytic efficiency (kcat/Km(H2O2)) of the cellulose peroxygenase reaction (kcat = 8.5 s−1, and Km(H2O2)=30μM) was an order of magnitude higher than that of the reductant (ascorbic acid) peroxidase reaction. The turnover of H2O2 in the ascorbic acid peroxidase reaction followed the ping-pong mechanism and led to irreversible inactivation of the enzyme with a probability of 0.0072. Using theoretical analysis, we suggest a relationship between the half-life of LPMO, the values of kinetic parameters, and the concentrations of the reactants.  相似文献   

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Studies are reported on the chemical reduction of the homobinuclear bis(μ-phosphido) metal complexes (CO)3Fe(μ-PR2)2Fe(CO)3 (R = Ph or Me), (NO)2-Fe(μ-PPh2)2Fe(NO)2 and (CO)4M(μ-PPh2)2M(CO)4 (M = Mo or W). Two reduction pathways have been observed which result in different two-electron transformations: (1) with Na or LiAlH4, electron transfer to yield the corresponding symmetric dianions of the type LnM(μ-PR2)2MLn2? without metalmetal bond and (2) with M′BR′3H(M′ = Li, Na, or K; R′ = Et or sec-Bu), hydride transfer to give monoanionic complexes of the type LnM(μ-PR2)(μ-L)MLn?1(PR2H)? or LnM(μ-PR2)MLn(PR2H)? (M = Fe, Mo, or W; L = CO or NO; R = Ph or Me). The monoanionic complexes can be deprotonated with n-BuLi at ?78 °C to the corresponding unsymmetric dianions LnM(μ-PR2)(μ-L)MLn?1(PR2)2? (M = Fe; L = CO or NO; R = Ph) or symmetric dianions LnM(μ-PR2)2MLn2? (M = Mo or W; L = CO; R = Ph). The unsymmetric dianions isomerize on slight warming to the symmetric dianions, which undergo protonation by CF3COOH to yield the aforementioned monoanions. Reactions of several members of these three classes of binuclear anions with CF3COOH, alkylating reagents, 1,1-diiodohydrocarbons and metal diiodo complexes have resulted in the synthesis of new binuclear and trinuclear compounds. Examples include (CO)3(H)Fe(μ-PPh2)Fe(CO)3(PPH2H), (CO)3Fe(μ-PPh2)(μ-C(R)O)Fe(CO)2(PPh2R) (R = Me, Et, n-Pr, or i-Pr), (CO)4M(μ-PPh2)2M(CO)3(C(R)Ome) (M = Mo or W; R = Me or Ph), (CO)2(η3?C3H5)Fe(μ?PPh2)?Fe(CO)3(PPh2C3H5), (CO)4M(μ?PPh2)2M(CO)3(C(R)Ome), (NO)2Fe(μ?CH2)(μ?Ph2PPPh2)Fe(NO)2, and Fe2Co(η5-C5H5)(CO)(NO)4(μ-PPh2)2. Synthetic and mechanistic studies on these reactions are presented.  相似文献   

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For a given graph G, ε(v) and deg(v) denote the eccentricity and the degree of the vertex v in G, respectively. The adjacent eccentric distance sum index of a graph G is defined as ξsv(G)=vV(G)ε(v)D(v)deg(v), where D(v)=uV(G)d(u,v) is the sum of all distances from the vertex v. In this paper we derive some bounds for the adjacent eccentric distance sum index in terms of some graph parameters, such as independence number, covering number, vertex connectivity, chromatic number, diameter and some other graph topological indices.  相似文献   

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