Membrane Partitioning: “Classical” and “Nonclassical” Hydrophobic Effects

The free energy of transfer of nonpolar solutes from water to lipid bilayers is often dominated by a large negative enthalpy rather than the large positive entropy expected from the hydrophobic effect. This common observation has led to the idea that membrane partitioning is driven by the “nonclassical” hydrophobic effect. We examined this phenomenon by characterizing the partitioning of the well-studied peptide melittin using isothermal titration calorimetry (ITC) and circular dichroism (CD). We studied the temperature dependence of the entropic (−TΔS) and enthalpic (ΔH) components of free energy (ΔG) of partitioning of melittin into lipid membranes made of various mixtures of zwitterionic and anionic lipids. We found significant variations of the entropic and enthalpic components with temperature, lipid composition and vesicle size but only small changes in ΔG (entropy–enthalpy compensation). The heat capacity associated with partitioning had a large negative value of about −0.5 kcal mol−1 K−1. This hallmark of the hydrophobic effect was found to be independent of lipid composition. The measured heat capacity values were used to calculate the hydrophobic-effect free energy ΔGhΦ, which we found to dominate melittin partitioning regardless of lipid composition. In the case of anionic membranes, additional free energy comes from coulombic attraction, which is characterized by a small effective peptide charge due to the lack of additivity of hydrophobic and electrostatic interactions in membrane interfaces [Ladokhin and White J Mol Biol 309:543–552, 2001]. Our results suggest that there is no need for a special effect—the nonclassical hydrophobic effect—to describe partitioning into lipid bilayers

УСЛОВИЯ ПЛАВЛЕНИЯ ГРАНИТОИДНЫХ КСЕНОЛИТОВ В КОНТАКТЕ СО ЩЕЛОЧНО‐БАЗИТОВОЙ МАГМОЙ (ГУСИНООЗЕРСКАЯ ДАЙКА, ЗАПАДНОЕ ЗАБАЙКАЛЬЕ): К ПРОБЛЕМЕ ПРОИСХОЖДЕНИЯ УЛЬТРАКАЛИЕВЫХ КИСЛЫХ РАСПЛАВОВ

The alkaline mafic (lamprophyric) Gusinoozerskaya dyke in West Transbaikalia is composed of partially melted granite xenoliths. Among the xenoliths, two melted substrates are observed: (1) plagioclase and quartz, and (2) alkaline feldspar and quartz. Few millimeters thick microfelsite and microgranophiric rims are the products of melting around the granite xenoliths. Ultra‐acid glass is observed in the inner parts of the xenoliths at the boundary of quartz and feldspars. A distinctive feature of the fresh melts (regardless of the composition of the protolithic sub‐ strate) is an increased content of potassium with K2O/Na2O≥2. Having compared the compositions of the products of contact melting with the experimental data, we conclude that melting took place in the presence of alkaline‐chloride and/or alkaline‐carbonic fluid released from the crystallizing host alkaline‐basic magma. The probable geotectonic conditions for the occurrence of ultrapotassic acid magmas are estimated.Щелочно‐мафическая (лампрофировая) Гусиноозерская дайка (Западное Забайкалье) содержит гранитные ксенолиты, испытавшие частичное плавление. Среди ксенолитов выявлено два субстрата, претерпевших плавление: 1) плагиоклаз и кварц и 2) щелочной полевой шпат и кварц. Продукты плавления представляют собой микрофельзитовые и микрогранофировые оторочки вокруг гранитных ксенолитов мощностью в первые миллиметры. Во внутренних частях ксенолитов на границе кварца и полевых шпатов наблюдается ультракислое стекло. Отличительной особенностью новообразованных расплавов, независимо от состава протолитового субстрата, является их повышенная калиевость с отношением K2O/Na2O≥2. На основе сопоставления составов производных контактового плавления с экспериментальными данными показано, что плавление происходило в присутствии щелочно‐хлоридного и/или щелочно‐углекислого флюида, выделявшегося из кристаллизующейся вмещающей щелочно‐основной магмы. Оценены вероятные геотектонические условия возникновения ультракалиевых кислых магм

ДІАГНОСТИКА СТАНУ ЕНДОМЕТРІЯ У ЖІНОК, ХВОРИХ НА ТУБЕРКУЛЬОЗ, У ПЕРІОД ПРЕГРАВІДАРНОЇ ПІДГОТОВКИ

The paper presents the results of examining of 33 patients of reproductive age afflicted with pulmonary tuberculosis. An analysis of functional and morphologic changes of the endometrium is adduced. It has been established that structural changes of the endometrium are conducive to noncarrying of pregnancy at early terms.Приведены результаты обследования 33 пациенток репродуктивного возраста, больных  туберкулезом легких. Проведен анализфункциональных и морфологических изменений эндометрия. Установлено, что структурные изменения эндометрия способствуют невынашиванию беременности в ранних сроках.Наведені результати обстеження 33 пацієнток репродуктивного віку, хворих на туберкульоз легень. Проведено аналіз функціональних та морфологічних змін ендометрія. Установлено, що структурні зміни ендометрія сприяють невиношуванню вагітності у ранніх термінах

MELTING CONDITIONS OF GRANITOID XENOLITHS IN CONTACT WITH ALKALINE MAFIC MAGMA (GUSINOOZERSKAYA DYKE, WESTERN TRANSBAIKALIA): TO THE PROBLEM OF THE ORIGIN OF ULTRAPOTASSIC ACID MELTS

The alkaline mafic (lamprophyric) Gusinoozerskaya dyke in West Transbaikalia is composed of partially melted granite xenoliths. Among the xenoliths, two melted substrates are observed: (1) plagioclase and quartz, and (2) alkaline feldspar and quartz. Few millimeters thick microfelsite and microgranophiric rims are the products of melting around the granite xenoliths. Ultra‐acid glass is observed in the inner parts of the xenoliths at the boundary of quartz and feldspars. A distinctive feature of the fresh melts (regardless of the composition of the protolithic sub‐ strate) is an increased content of potassium with K2O/Na2O≥2. Having compared the compositions of the products of contact melting with the experimental data, we conclude that melting took place in the presence of alkaline‐chloride and/or alkaline‐carbonic fluid released from the crystallizing host alkaline‐basic magma. The probable geotectonic conditions for the occurrence of ultrapotassic acid magmas are estimated