Two-step hard acid deprotection/cleavage procedure for solid phase peptide synthesis

A new two-step deprotection/cleavage procedure for t-butoxycarbonyl (Boc) based solid phase peptide synthesis is reported. First the protective groups are removed from 4-(oxymethyl)-phenylacetamidomethyl (PAM) resin attached peptide with the weak hard acid, trimethylsilyl bromide-thioanisole/trifluoroacetic acid (TFA). In the second step, the peptide is cleaved from the resin with a stronger hard acid such as trimethylsilvl trifluoromethanesulfonate in TFA or with HF. The method is also shown to deformylate Nⁱⁿ-formyltryptophan moiety efficiently. The usefulness of this procedure for practical solid phase peptide synthesis is demonstrated by comparison with other deprotection methods in the synthesis of urotensin II and human endothelin.     

Quantitative structure–activity relationship (QSAR) study of elastase substrates and inhibitors

One hundred Suc-X-Y-Ala-pNA peptides (SUC: succinyl, pNA: p-nitroanilide, X, Y: Gly, Ala, Val, Leu, Ile, Phe, Pro, x-aminobutyric acid, norvaline, norleucine) were synthesized and their reaction constants with porcine pancreatic elastase (K_m, K_cat and K_cat/K_m) were determined. These reaction constants were quantitatively analyzed using the Free–Wilson/Fujita–Ban method. The contribution of amino acid side chains to the reaction constants K_m, K_cat and K_cat/K_m), expressed logarithmically, was found to be additive. On the other hand, 19 elastase inhibitors of the general formula CF₃CO-X-Y-Ala-pNA (X,Y: ten amino acids) were synthesized, and their inhibition constants were compared with the Michaelis constant for the corresponding substrates and analyzed using free-energy-related substituent constants. In the analysis of amino acid side chains in the Y position, the K_i value of the inhibitor was generally correlated to the K_m value of the substrate, which corresponded to the inhibitor, thus confirming the validity of the equation This study may serve as a prototypical approach to unraveling structure–activity relationships of peptide substrates and inhibitors of medicinal or agricultural importance.     

Synthesis and conformation of the trimeric coiled-coil segment of laminin*

A disulfide linked 95-mer parallel hetero-trimeric active site segment of laminin was designed and synthesised. The three subunits, A (32-mer), B1 (30-mer) and B2 (33-mer), were prepared by Boc-based solid-phase peptide synthesis involving a two-step trimethylsilyl bromide-thioanisole and HF deprotection procedure. The interlinking of the three subunits was accomplished by the stepwise selective formation of two disulfide bridges using air-oxidation and thallium (III) trifluoroacetate oxidation. The conformations of the synthetic peptides were studied by circular dichroism (CD) spectroscopy, showing that the hetero-dimer, B1-B2, one of the homo-dimers, B1-B1, and the trinier are 30 to 40% in the α-helical conformation in aqueous buffer. Variable temperature CD studies demonstrated that the trimer is considerably more stable (melting temperature (Tm) = 61°) than the hetero-dimer, B1-B2 (Tm = 36°).     

An integrated approach to meta-analysis in alcohol studies*

The research design and methods utilised by the Collaborative Alcohol-Related Longitudinal Project are described. The project design addresses the critical need to develop procedures to assess the replicability of research results in alcohol studies. Key features of the research plan include: re-analysis of original data from multiple longitudinal studies of drinking behavior in the general population; centralization of all data analyses, developed and implemented by an interdisciplinary core staff; development of the research plan and interpretation of results in co-operation with original investigators of studies included in the project; and use of modeling procedures from meta-analysis to quantify the relative contribution of factors influencing the distribution of effect estimates across studies, including both methodological differences and aggregate level variables. The final section describes statistical methods for meta-analysis used by the project, including procedures for the calculation and combination of estimates of effect magnitude, categorical and continuous modeling procedures for use with effect sixes, and random effects models.     

A meta-analysis of life course variation in drinking*

Meta-analysis combines remits from multiple longitudinal studies to describe life course variation by age and sex for quantity of drinking per typical occasion (20 studies) and frequency of drinking during one month (27 studies). There is cross-study heterogeneity for the Time 1 means of the drinking variables blocking for age and sex. Age distributions for the Time I means are similar by gender within nations; in the aggregate, males exceed females in the magnitude of drinking. Dramatic shifts in the standarized mean difference (M₂ - M₁) occur among the young; greater homogeneity and moderate change (declines) occur later in life. Implicated in improving cross-study homogeneity for M ₂– M₁ among the young are interval between measurements, nation, Time 1 per capita consumption (PCC), difference in PCC and the Time 1 mean. Lower unstandardized regression coefficients are found for quantity among youth, but are not consistently homogeneous within nations; the association for frequency becomes increasingly stable with increasing age. Nation and interval are implicated in improving homogeneity. Decline in quantity occurs among the old. M₂-M₁, produces homogeneously higher regressions for groups of the young who increase quantity v. those who do not. Linkage of the group-level and individual-level findings is discussed.     

Preliminary results from a meta-analysis of drinking behavior in multiple longitudinal studies*

This paper introduces the scope and rationale of The Collaborative Alcohol-Related Longitudinal Project and describes the individual longitudinal studies which contribute to this large collaborative project, representing studies from 15 countries, It also serves as an introduction to four reports of the preliminary findings from the project. The project is distinguished by (I) its interdisciplinary research approach which has assembled a multidisciplinary group of scholars to direct and interpret analyses, (2) its use of primary data from multiple longitudinal studies, (3) the parallel analyses of primary data from multiple studies, using comparable measures across studies receded to a standard format and common analytic model, and (4) its use of meta-analysis to combine results across studies. Its research objectives include determining the cross-study consistency of findings of (1) the incidence and chronicity of drinking patterns and problems, (2) exogeneous factors which initiate and alter drinking careers, (3) socio-behavioral factors measured in childhood and adolescence which predict adult drinking problems, (4) inter-generational biological and social factors which predict adult drinking problems, and (5) aggregate-level factors which account for study differences. The method of sampling of studies from the world's alcohol-related general population longitudinal research is described.     

The correlation between surface microscopy and dermal histology in tetradecane-induced comedones in rabbit ear skin

Three concentrations of tetradecane and liquid paraffin were applied daily for 4 weeks to the external ear skin of rabbits, and the average diameter of the follicular lesions was measured under the Leitz MZ surface microscope. These observations showed that the increase in the size of follicular lesions with tetradecane was dose-dependent and the maximum diameter was reached on the 14th day. Serial biopsies were also taken for routine histology, and undiluted tetradecane was shown to produce follicular hyperkeratosis, microcomedones, closed comedones and open comedones. A good correlation was obtained between the surface observations and the histological findings. The surface microscope provides a simple and convenient in vivo method for evaluating comedo formation.     

Enhanced comedo formation in rabbit ear skin by squalene and oleic acid peroxides

The comedogenicity of UVA-irradiated and non-irradiated substances (squalene, oleic acid, tetradecane, isopropyl myristate, squalane and liquid paraffin) was evaluated by surface microscopy and histological examination after treating the ventral skin of rabbit ears with these substances. The lipid peroxide levels of these substances were also measured. Squalene itself was scarcely comedogenic but squalene peroxides were highly comedogenic. Both oleic acid and its peroxides were able to induce fairly large comedones and there was a good correlation between the lipid peroxide levels and the size of the comedones. The specimens biopsied from these comedones showed marked hyperplasia and hyperkeratosis of the epithelium in the follicular infundibulum and marked proliferation of the sebaceous glands. Although free fatty acids might play a role in the pathogenesis of acne, it is proposed that squalene and free fatty acids in sebum may be less comedogenic than their peroxides.     

A meta-analysis of depressive symptomatology and alcohol consumption over time*

Meta-analysis (eight general population longitudinal studies) describes the relationships (regressions) between quantity per occasion and depressive symptomatology over time. Quantity and depression are the strongest and most consistent predictors of final levels of themselves in all data sets. Age significantly and consistently predicts quantity for both sexes combined (the general pattern is replicated among males only). Depression significantly predicts quantity and quantity significantly predicts depression for females. Controlling for interval between measurements produces stronger prediction (more consistent over shorter intervals) for males. Depression only predicts quantity over longer intervals and quantity only predicts depression over shorter intervals for females. Explicit control for age found stronger relationships between initial and final measurement quantity, and depression for males. Quantity and depression significantly predict quantity and depression among young females. The relationship between quantify and depression among females illustrates the importance of controlling for age and sex. Methodological considerations are discussed.     

Analgesic and other pharmacological activities of a new narcotic antagonist analgesic (-)-1-(3-methyl-2-butenyl)-4-[2-(3-hydroxyphenyl)-1-phenylethyl]piperazine and its enantiomorph in experimental animals

Of 1-cyclohexyl-4-[2-(3-hydroxyphenyl)-1-phenylethyl]piperazine (I) and its 1-(3-methyl-2-butenyl) derivative (II), the S(+)-isomers were analgesically more active than either their R (-)-isomers or their racemates, having 15 to 44 times the potency of morphine in mice and rats. R (-)-I had comparable analgesic activity to morphine R (-)-II to pentazocine in mice, rats and dogs and they were nearly equipotent with pentazocine in reversing some actions of morphine. The S (+)-isomers and racemates lacked this action. R (-)-II required about 10 times more naloxone to reverse its analgesic activity than was needed to antagonise the S (+)-isomers, morphine and pentazocine. The S (+)-isomers and racemates produce a typical Straub tail reaction and increased spontaneous locomotor activity in mice, but the R (-)-isomers did not. R (-)-II had no significant physical dependence liability in mice, rats and monkeys. From these results, it is suggested that the compounds show an uncommon stereoselectivity in comparison with morphine and its surrogates, and that R (-)-II is worth investigating further as a narcotic antagonist analgesic.