Simplified active test of estimating tetanus toxoid]

The main purpose of these investigations was the comparison of two potency tests of Tetanus Toxoid. It was found that two doses test with reduced number of animals can be used in assay of different vaccines containing Tetanus component. One dose test is agreeable with requirements of WHO. It is credible and not complicated method of estimation Diphtheria and Tetanus Toxoids. This test required minimal number of animals.     

Interaction of fatty acid sodium salts with sodium deoxycholate

Interaction of homologous fatty acids (C3-C18) with sodium deoxycholate was investigated. From NMR and ultrasonic results it was found that short chain homologues (up to C9) do not participate in the formation of mixed micelles with sodium deoxycholate. Fatty acid homologues with longer chains (starting with C9) form mixed micelles by "burying" hydrophobic chains in hydrophobic environment of a sodium deoxycholate micelle.     

Xanthine:NAD+ oxidoreductase from embryo liver of hen Gallus gallus

1. Xanthine:NAD+ oxidoreductase from chick embryo liver is unconvertible to the O2-dependent form, as is the enzyme from the adult hen. The Km for NAD+ (approximately 3 microM) of the embryonic enzyme is equal to, and the Km for xanthine (approximately 5 microM) is 2.5-fold lower, when compared with respective Km values of the "adult" hen enzyme. The inhibition of embryonic enzyme by NADH begins at 10 microM NADH and attains 13% at 35 microM NADH (respective data for the "adult" enzyme: 50 microM and 20% at 80 microM NADH). 2. The course of hypoxanthine----xanthine----uric acid hydroxylation catalyzed by the embryonic and "adult" enzymes is similar, however the rate of the first reaction is 2-fold lower for the embryonic enzyme. Under conditions of the limited nutritional system in the developing chick embryo, the low rate of hypoxanthine hydroxylation may promote reutilization of hypoxanthine for nucleotide synthesis.     

Phylogenetic distribution in the genus Mus of t-complex-specific DNA and protein markers: inferences on the origin of t-haplotypes

We have examined the phylogenetic distribution of two t-specific markers among representatives of various taxa belonging to the genus Mus. The centromeric TCP-1a marker (a testicular protein variant specific for all t-haplotypes so far studied) has also been apparently detected in several non-t representatives of the Mus IVA, Mus IVB, and probably M. cervicolor species. By contrast, a t-specific restriction- fragment-length polymorphism allele (RFLP) of the telomeric alpha- globin pseudogene DNA marker alpha-psi-4 was found only in animals belonging to the M. musculus-complex species either bearing genuine t- haplotypes or, like the M. m. bactrianus specimen studied here, likely to do so. This t-specific alpha-psi-4 RFLP allele was found to be as divergent from the RFLP alleles of the latter, non-t, taxonomical groups as it is from Mus 4A, Mus 4B, or M. spretus ones. These results suggest the presence of t-haplotypes and of t-specific markers in populations other than those belonging to the M. m. domesticus and M. m. musculus subspecies, implying a possible origin for t-haplotypes prior to the radiation of the most recent offshoot of the Mus genus (i.e., the spretus/domesticus divergence), some 1-3 Myr ago.      

Drug recognition of DNA. Proposal for GC minor groove specific ligands: vinylexins

In a previous publication in this journal we have proposed an isolexin-like prototype of a GC minor groove specific ligand. The present paper is devoted to refinements of this prototype (increase in specificity and in DNA binding energy). It is shown that only a very limited improvement can be obtained by increasing the proton accepting capabilities of the heteroaromatic ring systems of the prototype, although these rings interact directly with the proton donating NH2 group of guanine. On the other hand a significant increase both in GC specificity and in DNA binding energy is obtained by replacing the NH linkers of the isolexin by C = C double bonds (yielding what we term "vinylexins"). Specificity is still largely conserved and the DNA binding energy is significantly increased in monocationic vinylexins, which should thus be efficient GC minor groove specific ligands. The outstanding importance for the GC specificity of the C = C linkers is evidenced by the disappearance of this specificity when these linkers are replaced by peptide bonds (peptilexins). On the other hand vinylexins with proton donating heteroaromatic rings are, as expected, AT specific. The vinylexin family may thus represent universal minor groove binding agents susceptible to bind to any given base pair sequence of DNA, following the positioning of their proton donor and proton acceptor rings. This study confirms the insufficiency of purely geometrical and/or hydrogen bonding considerations for the correct estimation of GC versus AT specificity of groove binding ligands. These can only be accounted for by taking into consideration the overall electronic properties of the interacting species and explicitly calculating the energies of complex formation including all the relevant contributions.     

A comprehensive classification of nucleic acid structural families based on strand direction and base pairing.

We propose a classification of DNA structures formed from 1 to 4 strands, based only on relative strand directions, base to strand orientation and base pairing geometries. This classification and its associated notation enable all nucleic acids to be grouped into structural families and bring to light possible structures which have not yet been observed experimentally. It also helps in understanding transitions between families and can assist in the design of multistrand structures.     

Theoretical exploration of netropsin binding to tRNA(Phe)

Theoretical exploration of the possible interaction of netropsin with tRNAPhe indicates that binding should occur preferentially with the major groove of the T psi C stem of the macromolecule, specifically with the bases G51, U52, G53 and phosphates 52, 53, 61 and 62. This agrees with the recent crystallographic result of Rubin and Sundaralingam. It is demonstrated that the difference with respect to netropsin binding with B-DNA, where it occurs specifically in the minor groove of AT sequences, is due to the differences in the distribution of the electrostatic molecular potential generated by these different types of DNA: this potential is sequence dependent in B-DNA (located in the minor groove of AT sequences and the major groove of GC sequences), while it is sequence independent and always located in the major groove in A-RNA. The result demonstrates the major role of electrostatics in determining the location of the binding site.     

The contractile basis of amoeboid movement: V. The control of gelation, solation, and contraction in extracts from dictyostelium discoideum

Motile extracts have been prepared from Dictyostelium discoideum by homogenization and differential centrifugation at 4 degrees C in a stabilization solution (60). These extracts gelled on warming to 25 degrees Celsius and contracted in response to micromolar Ca++ or a pH in excess of 7.0. Optimal gelation occurred in a solution containing 2.5 mM ethylene glycol-bis (β-aminoethyl ether)N,N,N',N'-tetraacetate (EGTA), 2.5 mM piperazine-N-N'-bis [2-ethane sulfonic acid] (PIPES), 1 mM MgC1(2), 1 mM ATP, and 20 mM KCI at ph 7.0 (relaxation solution), while micromolar levels of Ca++ inhibited gelation. Conditions that solated the gel elicited contraction of extracts containing myosin. This was true regardless of whether chemical (micromolar Ca++, pH >7.0, cytochalasin B, elevated concentrations of KCI, MgC1(2), and sucrose) or physical (pressure, mechanical stress, and cold) means were used to induce solation. Myosin was definitely required for contraction. During Ca++-or pH-elicited contraction: (a) actin, myosin, and a 95,000-dalton polypeptide were concentrated in the contracted extract; (b) the gelation activity was recovered in the material sqeezed out the contracting extract;(c) electron microscopy demonstrated that the number of free, recognizable F-actin filaments increased; (d) the actomyosin MgATPase activity was stimulated by 4- to 10-fold. In the absense of myosin the Dictyostelium extract did not contract, while gelation proceeded normally. During solation of the gel in the absense of myosin: (a) electron microscopy demonstrated that the number of free, recognizable F- actin filaments increased; (b) solation-dependent contraction of the extract and the Ca++-stimulated MgATPase activity were reconstituted by adding puried Dictyostelium myosin. Actin purified from the Dictyostelium extract did not gel (at 2 mg/ml), while low concentrations of actin (0.7-2 mg/ml) that contained several contaminating components underwent rapid Ca++ regulated gelation. These results indicated : (a) gelation in Dictyostelium extracts involves a specific Ca++-sensitive interaction between actin and several other components; (b) myosin is an absolute requirement for contraction of the extract; (c) actin-myosin interactions capable of producing force for movement are prevented in the gel, while solation of the gel by either physical or chemical means results in the release of F-actin capable of interaction with myosin and subsequent contraction. The effectiveness of physical agents in producting contraction suggests that the regulation of contraction by the gel is structural in nature.     

Theoretical study of ethidium intercalation in triple-stranded DNA and at triplex-duplex junctions.

The contribution of different factors in the interaction of ethidium intercalated into various sequences of a triple helix, or in the region of the junction between the double- and triple-stranded DNA has been studied by energy minimization. It is found that in the total energy of the ethidium- triple helix complexes, a particular electrostatic contribution emerges due to the presence of protonated cytosines in the triple helix. This parameters is determinant in the sequence-specificity of ethidium binding to the triple helix. The preferred intercalation sites of ethidium in the triple helix are proposed. The interaction of ethidium at the triplex-duplex junction, and its effects are also discussed. This study is aimed at searching for new drugs specific for the triple helix, or for the triplex-duplex junctions.