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Differential scanning calorimetry has been applied to aqueous suspensions comprised of synthetic phospholipids on whose chains reside substituents of diverse size (methyl, n-butyl, phenyl), polarity (alkyl, keto), number (one or both chains), and location (carbons 4, 6, 8, 10, 12, or 16 of 18-carbon chains). Attention focused primarily on the "main" phase transition in the lipid bilayers resulting from disordering ("melting") of the hydrocarbon tails. The thermotropic behavior revealed, among the more interesting observations, that alkyl groups at the center of the chains are far more disruptive than groups at either end. For example, distearoylphosphatidylcholine (DSPC) has a main transition temperature (Tf of 54.8 °C. Methyl substitution at carbons 4, 10, and 16 of the second chain gives Tc values of 41.5, 5.6, and 38.5 °C, respectively. Similarly, DSPC has a transition enthalpy, , of 10.6 kcal/mol. Methyl substitution at carbons 4, 10, and 16 of the second chain gives values of 8.8, 3.7, and 9.8 kcal/mol, respectively. This remarkable midchain effect is rationalized on a molecular basis and reconciled with earlier work by others showing that mobility is restricted in the first half of the chain after which motional freedom and disorder increase uniformly up to the terminal methyl. Systematic "structure-activity" studies of lipids, such as presented here, are important in testing membrane models and in controlling membrane properties through rational design of the synthetic lipids.dered state (below the transition temperature, Tc) to a more disordered, fluidlike state (above the Tc). Tracings of excess heat capacity vs temperature provide (a) Tc, the temperature at the maximum in the excess heat capacity profile, (b) ^, the total enthalpy associated with the transition, (c) MfvH, the van't Hoff enthalpy, and (d) / ^= CU, the cooperativity unit.Below rc, the "gel" phase has its hydrocarbon chains existing mainly in all-trans configurations. Both chain motion and the number of gauche linkages increase in the "liquid-crystal" phase

Resveratrol oligomers (REVs), a major class of stilbenoids, are biosynthesized by regioselective oxidative coupling of two to eight units of resveratrol monomer. Due to their unique structures and pleiotropic biological activities, natural product chemists are increasingly focusing on REVs in the last few decades. This study presents a detailed and thorough examination of REVs, including chemical structures, natural resources, and biological activities, during the period of 2010–2017. Ninety-two new REVs compounds, including 39 dimers, 23 trimers, 13 tetramers, six resveratrol monomers, six hexamers, four pentamers, and one octamer, have been reported from the families of Dipterocarpaceae, Paeoniaceae, Vitaceae, Leguminosae, Gnetaceae, Cyperaceae, Polygonaceae Gramineae, and Poaceae. Amongst these families, Dipterocarpaceae, with 50 REVs, accounts for the majority, and seven genera of Dipterocarpaceae are involved, including Vatica, Vateria, Shorea, Hopea, Neobalanocarpus, Dipterocarpus, and Dryobalanops. These REVs have shown a wide range of bioactivities. Pharmacological studies have mainly focused on potential efficacy on tumors, bacteria, Alzheimer’s disease, cardiovascular diseases, and others. The information updated in this review might assist further research and development of novel REVs as potential therapeutic agents.

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