Solid Tryptophan as a Pseudoracemate: Physicochemical and Crystallographic Characterization

The crystalline nature of solid tryptophan has been characterized by X‐ray single crystal and powder diffraction analyses, differential scanning calorimetry, as well as measurement of solid–liquid equilibrium in water/isopropanol solution. Both the thermodynamic and crystallographic investigations have demonstrated unambiguously that solid tryptophan crystallizes in the form of a pseudoracemate (i.e., solid solution) with maximum melting over the entire enantiomeric composition range. Comparative single‐crystal X‐ray studies show that the crystal structures of racemic and enantiomeric tryptophan give very similar solid‐state packing geometries dictated by hydrogen bonding interactions. Our results indicate that the insignificant difference between homochiral and heterochiral interactions accounts for the formation of a pseudoracemate for this system. Chirality 27:88–94, 2015. © 2014 Wiley Periodicals, Inc.     

Mixed monolayers of dipalmitoylglycerophosphocholine,distearoylglycerophosphocholine and 1-palmitoylglycerol

Mixed monolayer systems of dipalmitoylglycerophosphocholine (DPPC)-distearoylglycerophosphocholine (DSPC), palmitoylglycerol-DPPC, and palmitoylglycerol-DSPC have been investigated by a previously described thermodynamic treatment. The surface pressures of these systems were measured at various compositions and temperatures. The two-dimensional phase diagrams and the apparent molar entropy and energy changes were evaluated. It was found that the phase diagrams of the DPPC-DSPC, palmitoylglycerol-DSPC and palmitoylglycerol-DPPC systems are all of different types. According to our phase diagram classification, DPPC-DSPC, palmitoylglycerol-DSPC, and palmitoylglycerol-DPPC systems exhibited a modified cigar type, a eutectic type, and a negative azeotropic type, respectively.     

The steppes and deserts of the Xizang Plateau (Tibet)

The Xizang Plateau (Tibet) covers a vast area over 4 000 m with a severe environment. Steppes and deserts are widely distributed on the plateau to the west of 91.5°E. Poaceae, Asteraceae, Fabaceae and Cyperaceae are the most important families in the composition of steppe communities. The steppe can be divided into high-cold steppe and montane steppe. The former one is characterized by the Stipa purpurea community, which occupies a vast area with a cold, dry climate: annual mean temperature 0 to –6°C, annual rainfall is 150–300 mm; The latter one is distributed in some limited regions, where the climate is less severe: annual mean temperature 0–7°C, annual rainfall is 150–400 mm. The representative communities here are the Stipa glareosa and S. bungeana communities. Chenopodiaceae and Asteraceae play a principal role in both high-cold and montane deserts. The high-cold desert is unique. Its major representative is the Ceratoides compacta community, which is found at about 5 000 m, in an extremely cold and very dry climate. The Ceratoides latens and Ajania fruticulosa communities are the common ones of the montane desert which mainly appears below 4 600 m in elevation, where the annual temperature is about 0°C and the rainfall is less than 100 mm. The distribution of the steppe and the desert communities shows a clear regional differentiation, and an equally clear vertical distribution pattern.     

Thermotropism and hydration properties of POPE and POPE-cholesterol systems as revealed by solid state2H and31P-NMR

The partial phase diagram and the hydration properties of the 1-palmitoyl-2-oleoyl-phosphatidylethanolamine (POPE)-water system, in the absence and presence of 30 mol% cholesterol, have been investigated by solid state phosphorus NMR of the lipid and deuterium NMR of heavy water. The POPE-D₂O phase diagram resembles other phosphatidylethanolamine (PE)-water systems: below water-to-lipid molar ratios (R_i) of 3 the lamellar gel (L or L_c)-to-hexagonal type II (H_II) phase sequence is observed on increasing the temperature. For R_i3 the thermotropic sequence (L or L_c)-L-H_II is detected. On increasing hydration from R_i=3, the H_II phase is detected from 40°C to 85°C whereas the gel phase is observed from 40°C to 30°C. The limiting hydrations of the gel, L and H_II phases are R_i 3, 17 and 20, respectively. The number of bound water molecules per lipid is ca. 8 in both the La and HII phases. The presence of cholesterol stabilizes the hexagonal phase 20°C below temperatures at which it is observed in its absence and reduces the limiting hydration of the fluid and hexagonal phases to Ri 9 and 14, respectively. The structure and/or dynamics of the water bound to the interface are markedly modified on going from the L to the H_II phase.Abbreviations NMR Nuclear magnetic resonance - DDPE 1,2-Didodecyl-rac-glycerol-3-phosphoethanol-amine - DHPE 1,2-Dihexadecyl-sn-glycerol-3-phosphoethanol-amine - DOPE 1,2-Dioleoyl-sn-glycerol-3-phosphoethanol-amine - POPE 1-Palmitoyl-2-oleoyl-sn-glycerol-3-phosphoetha-nolamine - DAPE 1,2-Diarachinoyl-sn-glycerol-3-phosphoethanol-amine - DMPC 1,2-Dimyristol-sn-glycerol-3-phosphocholine - DPPC 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine - T_c lamellar gel-to-lamellar fluid transition temperature - T_h lamellar fluid-to-hexagonal transition temperature     

Effects of organic pH buffers on a cell growth and an antibody production of human-human hybridoma HB4C5 cells in a serum-free culture

Human-human hybridoma cells secreting a human monoclonal antibody were cultured in a serum-free medium containing various organic pH buffers in order to clarify their effects on cell growth and antibody production. Organic pH buffers having either one sulfonic acid and several acyclic amine moieties, or several cyclic amine moieties containing two amino nitrogen did not inhibit cell growth; while other organic buffers sulfonic acid moiety plus several cyclic amine moieties containing one amino nitrogen slightly decreased cell growth, but enhanced antibody production. Using Fujita's organic conceptual diagram, a relationship between the organicity and inorganicity of a pH buffer to cell growth and antibody production was found. pH buffers with large inorganicity and small organicity values were favorable for cell growth, and buffers with small inorganicity and large organicity values were preferred to enhance antibody production. Although the pH buffering range affects cell growth, its effect on antibody production is not clear. In conclusion, 2-morpholinoethanesulfonic acid (MES), 3-morpholino-propanesulfonic acid (MOPS) and 1, 2-N, N-bis[N, N-di(2-sulfonoethyl)piperazinyl]ethane (Bis-PIPES) are shown to be the most optimal of the buffers tested, because they enhanced antibody production without decreasing the cell growth among the pH buffers tested here.     

Life on the seafloor: adaptations and strategies in Stylophora (Echinodermata)

Stylophorans are a Palaeozoic group of non‐pentamerous echinoderms, morphologically well‐adapted to a benthic mode of life on soft sediment seafloors. By developing a thin and wide theca, they successively increased the surface area in contact with the substrate resulting in an even distribution of the body mass resting on the ground, and efficiently preventing the body from sinking into non‐indurated sediments (snowshoe strategy). In stylophorans, the body surface is dramatically increased in result of the expansion of two integumentary areas on the lower thecal surface. While infracentral areas are reduced in primitive forms to the detriment of massive marginals; in boot‐shape cornutes, infracentral areas are larger, polyplated and framed by very delicate marginals. In heart‐shaped cornutes, the reduction of both infracentral areas is compensated by the development of spiny elements on the theca outline. In forms where the degree of bilateral symmetry is high, the left infracentral area is larger than the right area, resulting in an elongated thecal shape. In structural geology, changes of shape of a rock submitted to a strain can be categorized by translating the obtained deformation into a strain ellipsoid plotted on a Flinn diagram, while in biology changes of shapes of organisms are traditionally measured through morphometric analysis. By applying Flinn's principle of strain ellipsoid to biological objects, the present study aims to characterize different life adaptations across stylophorans, observing changes of shape of both infracentral areas interpreted as two ellipsoids. Once plotted on a Flinn diagram, three significantly separated clusters are observed when focusing on the left area. This concerns forms with reduced infracentral areas, highly and weakly asymmetrical forms. According to these results, three new morphological adaptations are described (water strider, flat fish and stream‐lined body). These newly described adaptations enabled snowshoe strategist stylophorans to remain stable on top of the seafloor.     

A biometrical analysis of the South AmericanElymus glaucescens complex (Poaceae: Triticeae)

Based on a simple multivariate analysis of the morphology of theAgropyron pubiflorum complex—A. patagonicum, A. antarcticum, A. fuegianum, andA. magellanicum—the variation pattern is shown to be clinal, and all taxa are included in a single, variable species. Currently the majority of species ofAgropyron is included inElymus and the correct name of this species isE. glaucescens.     

Miscibility of phosphatidylcholine binary mixtures in unilamellar vesicles: Phase equilibria

Summary Miscibility among phospholipids with different lipid chain-lengths or with different head groups has attracted a number of research efforts because of its significance in biological membrane structure and function. The general consensus about the miscibility of phosphatidylcholines with varying lipid chainlengths appears to be that binary mixtures of phospholipids with a difference of two carbon atoms in the lipid chain mix well at the main phase transition. Miscibility between phosphatidylcholines with differences of four carbon atoms appears to be inconclusive. Previous reports on the phase transition of binary phospholipid mixtures are concerned mainly with multilamellar vesicles and are mostly limited to the main transition. In the present study, unilamellar vesicles were used and miscibility in binary systems between dimyristoyl-, dipalmitoyl- and distearoyl-phosphatidylcholines at pretransition, as well as main transition temperatures was evaluated by constructing phase diagrams. Two methods were used to monitor the phase transitions: differential scanning microcalorimetry and optical absorbance methods. The optical method has the advantage that unilamellar vesicles of dilute phospholipid concentrations can be used. The liquidus and solidus phase boundaries were determined by the onset temperature of heating and cooling scans, respectively, because the completion temperature of a phase transition has no meaning in binary solutions. Dimyristoyl- and distearoyl-phosphatidylcholines. where the difference in the, lipid chain-length is four carbon atoms, mixed well even at pretransition temperature.     

Ecosystem as circuits: diagrams and the limits of physical analogies

Diagrams refer to the phenomena overtly represented, to analogous phenomena, and to previous pictures and their graphic conventions. The diagrams of ecologists Clarke, Hutchinson, and H.T. Odum reveal their search for physical analogies, building on the success of World War II science and the promise of cybernetics. H.T. Odum's energy circuit diagrams reveal also his aspirations for a universal and natural means of reducing complexity to guide the management of diverse ecological and social systems. Graphic conventions concerning framing and translation of ecological processes onto the flat printed page facilitate Odum's ability to act as if ecological relations were decomposable into systems and could be managed by analysts external to the system.     

An empirical approach to the analysis of forest stratification

Natural forest communities are made up of different overlapping elementary subpopulations consisting of individuals of different species and ages. To stratify the individuals of a forest stand into elementary subpopulations by using tree height records, a graphical method was empirically proposed employing a derivative of Pearson's type VII distribution as a basis. Arranging all of the individual trees in a stand in the descending order of their height (x), and introducing the rank (N) of any individual in the ordered ranking ofx, finite difference (n) ofN and three values ofx, i.e.,x(N), x(N−n), andx(N+n) labelled byN, N−n, andN+n, respectively, the proposed method used the linear relation betweenx(N) and [x(N−n)+x(N+n)]. On thex(N) vs.[x(N−n)+x(N+n)] diagram, the relation between both the variables could be approximated by a few segmental linear relations and used for stratifying the individuals of a forest stand into subpopulations. The method was applied for analyzing the vertical stratification in forest stands of different forest formations in Japan, Southeast Asia, Africa, and South America. The conclusions on stratification which resulted from the proposed method corresponded well to the conclusions on stratification from profile diagrams.