Comparison of physico-chemical properties of two forms of dopamine-beta-hydroxylase from chromaffin granules

The purification procedures of both soluble and membrane-bound forms of dopamine-beta-hydroxylase have been developed. The membrane-bound form was solubilized by a detergent. Both preparations have been obtained in electrophoretically homogeneous form. The yield of soluble and membrane-bound enzyme forms by a described procedure was 22 mg and 15 mg, correspondingly, from 100 g of chromaffin granules paste. A comparative analysis of the main physico-chemical properties of the two enzyme forms has shown their identity. The effects of pH, ionic strength, oxidants and reducers on the EPR spectra of the two forms of dopamine-beta-hydroxylase have been investigated. A comparison of the EPR spectra of the two forms of the enzyme suggests that the copper environment of soluble and membrane-bound dopamine-beta-hydroxylases is practically identical.     

The theory of phyllotaxis. II. Crystallographic interpretation of the interrelation between lower and superior phyllotaxis forms

Cross-opposite phyllotaxis forms are defined as superior with respect to the alternate ones and verticillate phyllotaxis forms as superior with respect to the opposite ones. Different phyllotaxis forms can be interpreted as a result of stretching of crystal-like structures of the embryo formed by dense packing of rudiments. Based on hypothetical concepts of the properties of plant rudiments and embryos, possible mechanisms of the formation of superior phyllotaxis forms from the lower ones have been analyzed. It was shown that the superior phyllotaxis forms can be considered as the results of additive summation of the lower forms. The theoretical conclusions are confirmed by the examples of polymorphic phyllotaxis in conspecific plants and by the facts of accidental splitting of superior phyllotaxis forms into the corresponding lower forms in nature and in experiment. The mechanisms underlying the formation of multiple forms of helical phyllotaxis have been proposed. The concept of a new type of mixed hexagonal-tetragonal phyllotaxis has been formulated and the mechanism of its formation has been considered. The forms of corn grain packaging in the corncob and leaf arrangement on the strawberry tomato stem are given as examples of true hexagonal-tetragonal phyllotaxis in nature.     

Rational design of carbonitrile-carboxaldehyde cation receptor models: probing the nature of the heteroatom–metal interaction

Amino acids are constituents of proteins and enzymes which take part almost in all metabolic reactions. Glutamic acid, with an ability to form a negatively charged side chain, plays a major role in intra and intermolecular interactions of proteins, peptides, and enzymes. An exhaustive conformational analysis has been performed for all eight possible forms at B3LYP/cc-pVTZ level. All possible neutral, zwitterionic, protonated, and deprotonated forms of glutamic acid structures have been investigated in solution by using polarizable continuum model mimicking water as the solvent. Nine families based on the dihedral angles have been classified for eight glutamic acid forms. The electrostatic effects included in the solvent model usually stabilize the charged forms more. However, the stability of the zwitterionic form has been underestimated due to the lack of hydrogen bonding between the solute and solvent; therefore, it is observed that compact neutral glutamic acid structures are more stable in solution than they are in vacuum. Our calculations have shown that among all eight possible forms, some are not stable in solution and are immediately converted to other more stable forms. Comparison of isoelectronic glutamic acid forms indicated that one of the structures among possible zwitterionic and anionic forms may dominate over the other possible forms. Additional investigations using explicit solvent models are necessary to determine the stability of charged forms of glutamic acid in solution as our results clearly indicate that hydrogen bonding and its type have a major role in the structure and energy of conformers.     

Multiple molecular forms of glutamine synthetase in pea seeds

Summary Multiple molecular forms of glutamine synthetase (GS, EC 6.3.1.2) have been studied in pea seeds of different varieties. The number of GS molecular forms in the seeds proved to be related to their colour. Two GS forms in the green seeds have been found and only one of them in the yellow seeds. Green seeds had chlorophyll content amounted to 0.4% of the total pigment content in the leaves. Chloroplasts, somewhat smaller than those in pea leaves of the same variety, have been isolated from green seeds. The presence of the second GS form in the pea green seeds we relate to the chloroplasts. By electrophoretic mobility both forms of GS from the green seeds are not identical to the chloroplast GS and the cytosol GS of leaves. Thus, we believe pea plant to contain, at least, four GS forms.     

Structural and thermodynamic analysis of conformational states of self-complementary deoxyhexanucleotides 5'-d(GpCpApTpGpC) and 5'-d(GpCpTpApGpC) in aqueous solution

The conformational states of the self-complementary deoxyhexanucleotides d(GCATGC) and d(GCTAGC) capable of forming hairpin structures in aqueous solution have been studied by one- and two-dimensional 1H NMR spectroscopy and molecular dynamics simulations. The equilibrium thermodynamic parameters of the formation of duplex and hairpin forms have been determined, and the spatial structures of the d(GCATGC) and d(GCTAGC) conformers have been calculated. A comparative analysis of the thermodynamic and conformational parameters of self-association has been made. The molecular dynamics of the hexamer forms in the nanosecond time scale has been studied, and the mobility of their structural constituents has been evaluated. Possible reasons for the observed distinction in the thermodynamic stability of duplex and hairpin forms of the deoxyhexanucleotide sequences are discussed.     

Determination of irinotecan (CPT-11) and its active metabolite SN-38 in human plasma by reversed-phase high-performance liquid chromatography with fluorescence detection

Sensitive high-performance liquid chromatographic assays have been develope to determine the levels of the lactone and lactone plus carboxylate (total) forms of the antitumor agent irinotecan (CPT-11) and its active metabolite SN-38, in human plasma. The related compound camptothecin was used as the internal standard. The selective sample pretreatment for the lactone forms involved a single solvent extraction with acetonitrile-n-butyl chloride (1:4,v/v), whereas the sample clean-up for the total forms was a simple protein precipitation with aqueous perchloric acid-methanol (1:1, v/v), which results in the conversion of the carboxylate to the lactone forms. Chromatography was carried out on a Hypersil ODS column, with detection performed fluorimetrically. The methods have been validated, and stability tests under various conditions have been performed. The lower limits of quantitation are 0.5 and 2.0 ng/ml for the lactone and total forms, respectively. The assays have been used in a single pharmacokinetic experiment in a patient to investigate the applicability of the method in vivo.     

福建省绞股蓝资源植物

本文介绍了福建省资源植物绞股蓝的生长环境,分布和利用。1985年以来我们采集了许多野生类型绞股蓝在厦门种植,并选出一些优良类型。     

Evolution of complex fruiting-body morphologies in homobasidiomycetes

The fruiting bodies of homobasidiomycetes include some of the most complex forms that have evolved in the fungi, such as gilled mushrooms, bracket fungi and puffballs ('pileate-erect') forms. Homobasidiomycetes also include relatively simple crust-like 'resupinate' forms, however, which account for ca. 13-15% of the described species in the group. Resupinate homobasidiomycetes have been interpreted either as a paraphyletic grade of plesiomorphic forms or a polyphyletic assemblage of reduced forms. The former view suggests that morphological evolution in homobasidiomycetes has been marked by independent elaboration in many clades, whereas the latter view suggests that parallel simplification has been a common mode of evolution. To infer patterns of morphological evolution in homobasidiomycetes, we constructed phylogenetic trees from a dataset of 481 species and performed ancestral state reconstruction (ASR) using parsimony and maximum likelihood (ML) methods. ASR with both parsimony and ML implies that the ancestor of the homobasidiomycetes was resupinate, and that there have been multiple gains and losses of complex forms in the homobasidiomycetes. We also used ML to address whether there is an asymmetry in the rate of transformations between simple and complex forms. Models of morphological evolution inferred with ML indicate that the rate of transformations from simple to complex forms is about three to six times greater than the rate of transformations in the reverse direction. A null model of morphological evolution, in which there is no asymmetry in transformation rates, was rejected. These results suggest that there is a 'driven' trend towards the evolution of complex forms in homobasidiomycetes.     

Parkinson's disease: a genetic perspective

Parkinson's disease (PD) is a common neurodegenerative disorder in the aging population, affecting more than 1% over the age of 65 years. Certain rare forms of the disease are monogenic, representing 5-10% of PD patients, but there is increasing evidence that multiple genetic risk factors are important also for common forms of PD. To date, 13 genetic loci, PARK1-13, have been suggested for rare forms of PD such as autosomal dominant and autosomal recessive PD. At six of these loci, genes have been identified and reported by several groups to carry mutations that are linked to affected family members. Genes in which mutations have been linked to familial PD have also been shown to be candidate genes for idiopathic forms of PD, as those same genes may also carry other mutations that merely increase the risk. Four of the PARK genes, SNCA at PARK1, UCH-L1 at PARK5, PINK1 at PARK6 and LRRK2 at PARK8, have been implicated in sporadic PD. There are indeed multiple genetic risk factors that combine in different ways to increase or decrease risk, and several of these need to be identified in order to begin unwinding the causative pathways leading to the different forms of PD. In this review, we present the molecular genetics of PD that are understood today, to help explain the pathways leading to neurodegeneration.     

Cell-cell interactions during formation and reactivation of "nonculturable" mycobacteria

To date, the possible existence of "nonculturable" (NC) but potentially viable forms has been shown for some bacteria. NC mycobacteria have attracted particular interest due to the assumption that the latent form of tuberculosis is associated with the conversion of its causative agent, Mycobacterium tuberculosis, into the NC state. A number of approaches have been developed to obtain NC forms of mycobacteria, but the mechanisms of transition into or from this state have been insufficiently studied. This review considers cell-cell communications involved in the formation and reactivation of NC forms of the bacteria M. smegmatis and M. tuberculosis. Special attention has been paid to the secreted Rpf family proteins, which belong to peptidoglycan hydrolases and participate in the resuscitation of NC mycobacteria.     

Actinosporean infections in oligochaetes in a river system in southwest Ireland with descriptions of three new forms

Sediment samples were collected in April, June and August 1998 from a river in southwest Ireland. A total of 1,836 oligochaete specimens were collected from these sediments, and examined for actinosporean infections. Actinosporean-infected oligochaetes have been determined, symptoms and course of infection have been considered and the spores released from them have been described. Spore characteristics for each actinosporean were defined and the prevalence of infection in each oligochaete species was also determined. The overall prevalence of infection with actinosporeans within the oligochaete sample was approximately 2%. Seven types were distinguished, belonging to echinactinomyxon, aurantiactinomyxon and neoactinomyxum forms, from Tubifex ignotus, Lumbriculus variegatus and Limnodrilus hoffmeisteri, and compared with actinosporean types previously reported in the literature. Three of these forms have not been previously described, while the other 4 are morphologically and morphometrically similar to known forms. These actinosporeans may be stages in myxozoan life cycles.     

Collagenase sensitivity and aggregation properties of Electrophorus acetylcholinesterase.

Tailed forms of Electrophorus acetylcholinesterase, mainly A (9 S) and C (14.2 S) forms, have been subjected to collagenase treatment. Several steps have been identified, yielding molecules which have lost different portions of the tail, and eventually resulting in separation of the isolated tetramers. These modifications result in the disappearance of the low-ionic strength aggregating properties. The molecules which have retained relatively large fragments of the tail do not aggregate in the same conditions as the intact forms, but still form small aggregates in the presence of high levels of polyanions. A model of the tailed molecules, illustrating the existence of discrete collagenase-sensitive regions in the tail, is discussed.     

Two forms of pyruvate kinase in Escherichia coli. A comparison of chemical and molecular properties.

The two forms of pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) present in Escherichia coli have been purified from the same cultures and crystallized. A modified procedure for the purification of type I pyruvate kinase is described. Molecular weight, subunit structure, amino acid composition, NH2-terminal amino acid, maps of tryptic peptides and conditions for crystallization have been determined for the two forms. A comparison of these data shows that the two forms are different proteins, each being a tetramer of identical subunits.     

Crystallization and preliminary X-ray diffraction analysis of oucleoside diphosphate kinase from Myxococcus xanthus.

Nucleoside diphosphate (NDP) kinase catalyzes the transfer of the gamma-phosphate from a nucleoside triphosphate to a nucleoside diphosphate. Human and rodent forms of this enzyme have been shown to be suppressors of metastasis. Crystals that diffract X-rays to high resolution have been obtained for the recombinant Myxococcus xanthus NDP kinase expressed in and purified from Escherichia coli. Two crystal forms have been obtained. Both forms are orthorhombic, space group I222 (or I2(1)2(1)2(1)) with a = 267.1 A, b = 74.0 A and c = 75.1 A for form I and a = 53.5 A, b = 74.0 A and c = 75.1 A for form II. Form I appears to have five molecules in the asymmetric unit approximately related to each other by a translation of 0.2 along the a axis. Diffraction data have been recorded to 1.9 A for form I and to 2.2 A for form II.     

Theoretical analysis of conformations of Ac-Gly-L-Ala-Gly-NHMe with intramolecular hydrogen bonds

The hydrogen-bonded structures of Ac-Gly-L -Ala-Gly-NHMe have been studied by theoretical conformational analysis. The geometric parameters and energies of stable forms with various combinations of 3 → 1 and 4 → 1 type hydrogen bonds have been calculated. The stable conformations found can be used as canonical forms in the investigation of linear and cyclic peptide compounds with intramolecular hydrogen bonds.     

Properties and characterization of soluble forms of lymphocyte acetylcholinesterase from an ox

Two soluble forms of AChE from lymphocyte membrane have been obtained, the Triton solubilized Sd form and the high molar salt solubilized Ss form. They present similar Km (0.10 mM). Hydrodynamic properties of these forms have been studied on saccharose gradients with and without detergent or salt. A similar sedimentation coefficient has been found for these two forms (5.7 S). Lymphocyte plasma membrane AChE is a dimeric form (G2). Without detergent, the Sd form shows multiple secondary forms due to main form polymerization. Increase of NaCl concentration (2M) gives rise to a partial dissociation of these polymers. In the same conditions, the Ss form is not affected. The Ss form centrifugated on cesium chloride gradient has a higher density than the Sd form. These two forms have been treated by HPLC: the Stokes radii are respectively 7.1 nm for the Sd form and 4.5 nm for the Ss form. The molecular weights have been estimated at 175 000 for the Sd form and 105 000 for the Ss form. Pronase enzymatic digestion shows that the Ss form is more rapidly inactivated than the Sd form. Phospholipase C inhibits the Ss form and indicates that this form is a lipid-enzyme complex. The Sd form presents a different behaviour: this form is first activated, and afterwards inhibited by phospholipase C. This behaviour could be due to a more preponderant lipidic environment for the Sd form. The Sd form is probably a detergent-lipid-enzyme complex with an important hydrophobocity. These two forms can be explained by a different association between the enzyme and the phospholipids at the plasma membrane.     

Chloroplast translational initiation factor 3. Purification and characterization of multiple forms from Euglena gracilis.

The chloroplast translational initiation factor 3 (IF-3chl) has been purified by a combination of gravity and high pressure liquid chromatographic steps. IF-3chl activity has been resolved into three forms designated alpha, beta, and gamma. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates that the alpha form corresponds to a single polypeptide with a molecular mass of approximately 34 kDa. The beta and gamma forms have been purified to near homogeneity, and both forms appear to function as monomers with molecular masses of about 39-42 kDa. All three forms are heat stable. All the forms of IF-3chl detected enhance the poly (A,U,G)-dependent binding of the initiator tRNA to chloroplast 30 S ribosomal subunits in the presence of Escherichia coli IF-1 and IF-2. The chloroplast factor, unlike the corresponding bacterial factor, does not have a strong RNA binding activity.