试论颌的起源与演化

以动物进化为主线,论述了颌的起源和由无颌脊椎动物到颌口类颌的演化过程,并对颌的结构及其它鳃弓的演化进行了概述。     

The composition of the lipid globules of Ilex aquifolium leaves and its variability with the age of the leaf and with season

The cytoplasmatic globules of Ilex aquifolium L. mainly consist of fatty acid esters of the triterpenoid alcohols α and β-amyrin. In very young leaves these are practically only palmitates. With increasing leaf age, increasing amounts of saturated and unsaturated C18 acids were found with comparatively high amounts of linoleic and linolenic acid in leaves of one year and older. Some accumulation of the triterpene precursor squalene was also observed with increasing age of the leaves. In addition to age effects, seasonal changes occur too. Independent of the age of the leaf, an increase in palmitic acid and a decrease in linoleic and especially linolenic acid was observed in the winter in mature leaves.     

Advancement in the derivatizations of the amino groups with the o-phthaldehyde-thiol and with the 9-fluorenylmethyloxycarbonyl chloride reagents

An overview is presented on the advancement of the two most frequently used derivatization protocols applying the o-phthalaldehyde (OPA)-thiol and the fluorenylmethyloxycarbonyl (FMOC) chloride reagents, prior to the high performance liquid chromatographic analysis of amino acids. This review pays special attention (i) to the blank value, to the composition, to the stability and to the life time of the reagents, (ii) to the optimum pH conditions for the interactions and derivatives' elutions, (iii) to the characteristics and behavior of those amino acids which might provide more than one derivative correlating with the molar ratios of the reagent to the reactants, and (iv) on the practical applicability of the optimized protocols.     

Interaction of calmodulin with the red cell and its membrane skeleton and with spectrin

The binding of calmodulin to red cell membrane cytoskeletons and to purified spectrin from red cells and bovine brain spectrin (fodrin) has been examined. Under physiological solvent conditions binding can be measured by ultracentrifugal pelleting assays. The membrane cytoskeletons contained a single class of binding sites, with a concentration similar to that of spectrin dimers and an association constant of 1.5 X 10(5) M-1. Binding is calcium dependent and is suppressed by the calmodulin inhibitor trifluoperazine. The binding showed a marked dependence on ionic strength, with a maximum at 0.05 M, and a steep dependence on pH, with a maximum at pH 6.5. It was unaffected by 5 mM magnesium. An azidocalmodulin derivative, under the conditions of our experiments, did not label the spectrin-containing complex, although it could be used to demonstrate binding to fodrin. Binding of calmodulin to spectrin tetramers and fodrin in solution could be demonstrated by a pelleting assay after addition of F-actin. Calculations (which are necessarily rough) suggest that at the free calcium concentration prevailing in a normal red cell about 1 in 20 of the calmodulin binding sites in spectrin will be occupied; this proportion will rise rapidly with increasing intracellular calcium. To determine whether inhibition of calmodulin binding to red cell proteins disturbs the control of cell shape, as has been suggested, calcium ions were removed from the cell by addition of an ionophore and of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid to the external medium. This did not affect the discoid shape. Trifluoperazine still induced stomatocytosis, exactly as in untreated cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interaction of trichorzianines A and B with model membranes and with the amoeba Dictyostelium

Trichorzianines A (TA) and B (TB) are microheterogeneous mixtures of antibiotic nonadecapeptides of the peptaibol class which interact with lipidic membranes and modify their permeability properties. The TB differ from the TA by replacement of the Gln-18 by a Glu, giving rise to a C-terminal negative charge at neutral pH. The role of this charge on the trichorzianine-lipid interaction was investigated with model membranes by fluorescence spectroscopy and the results were correlated with the biological activity toward the amoeba Dictyostelium discoideum. The interaction of the acidic trichorzianine TB IIIc (Glu-18) with phospholipid bilayers and the subsequent induced permeability were weaker than that exhibited by the uncharged TA IIIc (Gln-18) and MeTB IIIc (TB IIIc monomethyl ester). The unfavourable effect of the negative charge in TB IIIc was strongly enhanced by incorporation of cholesterol in the bilayer. Similarly, TA IIIc as well as MeTB IIIc induced growth inhibition and lysis of the amoeba Dictyostelium at four times lower concentrations than TB IIIc. The results suggested that the interaction of trichorzianines with the phospholipid bilayer and the subsequent modifications of permeability were involved in the inhibitory properties and cell lysis induced by trichorzianines toward Dictyostelium.     

Investigation of the structural basis of the interaction of calpain II with phospholipid and with carbohydrate.

Two forms of pig kidney calpain II were isolated, both of which appeared to contain an intact 80 kDa large subunit, but which showed specific proteolytic degradation at the N-terminal end of the 30 kDa small subunit. The structure of each of these molecules was investigated by amino acid sequence analysis. The forms corresponded to molecules with small subunits starting at residue 38 (degraded calpain A) and at residue 62 (degraded calpain B) of the complete sequence. These molecules were tested for their ability to interact with phosphatidylinositol and with carbohydrate (agarose gel-filtration media). Calpain and degraded calpain A, but not degraded calpain B, would interact with phosphatidylinositol. Thus the sequence (G)17TAMRILG (residues 38-61) is essential for the interaction. Neither calpain nor the degraded forms of the enzyme showed specific interaction with carbohydrate.     

产漆酶菌株筛选及一株产酶菌株的优化与鉴定

【目的】从26株真菌菌株中筛选高产漆酶菌株。【方法】采用愈创木酚法进行产漆酶菌株的筛选,通过正交实验对筛选出的高产菌株进行优化,并通过形态学和分子系统学对菌株进行鉴定。【结果】26株真菌菌株中有4株可产生漆酶,其中菌株H52.1为产漆酶最好菌株;菌株H52.1产漆酶优化培养基碳源为可溶性淀粉,氮源为硝酸铵,pH为8,金属离子为Ca2+;经鉴定,该菌株为大孢戴氏霉。【结论】大孢戴氏霉在产漆酶方面值得进一步研究开发。     

Cellular and metabolic specificity in the interaction of adhesion proteins with collagen and with cells

Fibronectin mediates the adhesion of fibroblasts to collagen substrates, binding first to the collagen and then to the cells. We report here that the interaction of the cells with the fibronectin-collagen complex is blocked by specific gangliosides, GD_{1 a} and GT₁, and that the sugar moieties of these gangliosides contain the inhibitory activity. The gangliosides act by binding to fibronectin, suggesting that they may be the cell surface receptor for fibronectin. Evidence is presented that other adhesion proteins or mechanisms of attachment exist for chondrocytes, epidermal cells, and transformed tumorigenic cells, since adhesion of these cells is not stimulated by fibronectin. Chondrocytes adhere via a serum factor that is more temperature-sensitive and less basic than fibronectin. Unlike that of fibroblasts chondrocyte adhesion is stimulated by low levels of gangliosides. Epidermal cells adhere preferentially to type IV (basement membrane) collagen but at a much slower rate than fibroblasts or chondrocytes. This suggests that these epidermal cells synthesize their own specific adhesion factor. Metastatic cells cultured from the T241 fibrosarcoma adhere rapidly to type IV collagen in the absence of fibronectin and do not synthesize significant amounts of collagen or fibronectin. Their growth, in contrast to that of normal fibroblasts, is unaffected by a specific inhibitor of collagen synthesis. These data indicate the importance of specific collagens and adhesion proteins in the adhesion of certain cells and suggest that a reduction in the synthesis of collagen and of fibronectin is related to some of the abnormalities observed in transformed cells.     

Studies on the interaction of tiamulin with the phospholipids in model membranes and with microsomes.

The drug tiamulin interacts with phospholipid membranes mainly in a nonelectrostatic way. At pH-values where the drug possesses a net positive charge only small binding is observed. In the presence of cholesterol tiamulin is excluded from the membranes. The interaction of tiamulin with membranes cannot be explained by a simple partitioning but is governed by structural rearrangements of the lipid phase. At low drug concentrations we observe sigmoidal binding characteristics in the rigid as well as in the fluid state up to a level of about 2-3 mol drug bound per 1000 mol phospholipid. The range in which this cooperative interaction occurs can be compared with the drug concentration in the erythrocyte membrane which protects from hypotonic lysis. Further addition of tiamulin to the rigid membrane leads to fluidization. Saturation of the membranes with tiamulin is completely in parallel to their fluidization. The relevance of the cooperative interaction at low drug concentration and of the subsequent fluidization at elevated concentration for the microsomal membrane is discussed.