Effect of water activity on the mechanical glass transition and dynamical transition of bacteria

The purpose of this study was to clarify the glass-transition behavior of bacteria (Cronobacter sakazakii) as a function of water activity (a_w). From the water sorption isotherm (298 K) for C. sakazakii, monolayer water content and monolayer a_w were determined to be 0.0724 g/g-dry matter and 0.252, respectively. Mechanical relaxation was investigated at 298 K. In a higher a_w range of over 0.529, the degree of mechanical relaxation increased with an increase in a_w. From the effect of a_w on the degree of mechanical relaxation, the mechanical a_wc (a_w at which mechanical glass transition occurs at 298 K) was determined to be 0.667. Mean-square displacement of atoms in the bacteria was investigated by incoherent elastic neutron scattering. The mean-square displacement increased gradually with an increase in temperature depending on the a_w of samples. From the linear fitting, two or three dynamical transition temperatures (low, middle, and high T_ds) were determined at each a_w. The low-T_d values (142–158 K) were almost independent from a_w. There was a minor effect of a_w on the middle T_d (214–234 K) except for the anhydrous sample (261 K). The high T_d (252–322 K) largely increased with the decrease in a_w. From the a_w dependence of the high T_d, the dynamical a_wc was determined to be 0.675, which was almost equivalent to the mechanical a_wc. The high T_d was assumed to be the glass-transition temperature (T_g), and anhydrous T_g was estimated to be 409 K. In addition, molecular relaxation time (τ) of the bacteria was calculated as a function of a_w. From the result, it is suggested that the progress of metabolism in the bacterial system requires a lower τ than approximately 6 × 10^?5 s.     

Low frequency and diffusive motion in aligned phospholipid multilayers studied by pulsed NMR

Measurements of T₁, T_1?, T_1D and the FID are reported for protons in aligned stacks of Egg Yolk Lecithin (EYL)-D₂O multilayers. From the ω₁ dependence of T_1? and the ω₀ dependence of T₁ the two dispersive regions of the spectral density function were identified. The lower frequency region has a centre angular frequency of 2.2 × 10⁵ rad/s and the upper frequency region a centre angular frequency of 4 × 10⁷ rad/s.From the orientation dependence of T_1?, T_1D and the FID, the lower frequency dispersion is assigned to fluctuations in the packing density of the hydrocarbon chains in the plane of the bilayer, and the upper frequency region to the translational diffusion of the lipid molecules. Based on a similar approach to one previously described, a diffusion coefficient of 1.4 × 10^?8 cm²/s is calculated for the EYL molecules in the bilayers.     

New butenolides from Aspergillus terreus

From the culture filtrate of Aspergillus terreus, seven related yellow substances were isolated and the simplest, C₁₇H₁₂O₅, was proved to be 3-(p-hydroxyphenyl)-4-hydroxy-5-(p-hydroxybenzylidene)-2(5H)-furanone.     

The temperature properties of human α2-macroglobulin in the range −15 to +37°C. An investigation of supercooled solutions using small-angle X-ray scattering and dilatometry

The effect of temperature on human α₂-macroglobulin dissolved in a water buffer containing 0.0065 m NaH₂PO₄ and 0.0652 m Na₂HPO₄ pH 7.78, has been investigated in the range ?15°C (supercooled water solutions) to +37°C using small-angle X-ray scattering and dilatometry. From the small-angle X-ray data it follows that there is no detectable change in conformation, or outer dimensions, of α₂-macroglobulin as a function of temperature. There is, however, a marked increase in the scattering power of the samples at decreasing temperature and vice versa. From measurements of the influence of the temperature on the apparent specific volume, using dilatometry, it follows that dv₁/dt = 0.00055 cm³g^?1K^?1, and the influence of the temperature on the scattering power can be fully explained by this value. In order to explain this obvious paradox, that there is a change in the apparent specific volume of α₂-macroglobulin without any accompanying change in the outer dimensions, we propose that there is also a change in the internal hydration of the protein as a function of temperature. Decreasing temperature leads to an increased hydration and vice versa.     

Gibberellins in Embryo-Suspensor of Phaseolus coccineus Seeds at the Heart Stage of Embryo Development

Gibberellins (GAs) in suspensors and embryos of Phaseolus coccineus seeds at the heart stage of embryo development were analyzed by combined gas chromatography-mass spectrometry (GC-MS). From the suspensor four C₁₉-GAs, GA₁, GA₄, GA₅, GA₆, and one C₂₀ GA, GA₄₄, were identified. From the embryo, five C₁₉-GAs GA₁, GA₄, GA₅, GA₆, GA₆₀ and two C₂₀ GAs, GA₁₉ and GA₄₄ were identified. The data, in relation to previous results, suggest a dependence of the embryo on the suspensor during early stages of development.     

AMPHOTERIC BEHAVIOR OF COMPLEX SYSTEMS : IV. NOTE ON THE ISOELECTRIC POINT AND IONIZATION CONSTANTS OF SULFANILIC ACID.

From the solubility minimum the value of the basic ionization constant of sulfanilic acid is shown to lie probably between the values 1.7 x 10^–15 and 3.2 x 10^–15. From solubility measurements the value of this same constant is shown to lie probably between 2.0 and 2.2 x 10^–15, and the isoelectric point of sulfanilic acid is thus at a cH of 0.056 or a pH of 1.25. From conductivity ratios the acid ionization constant of sulfanilic acid is shown to be 7.05 x 10^–4 at room temperature (21°C.). Calculations are made, from data published in preceding papers, of the ionization constants of glycine, K_a being 2.3 x 10^–10, and K_b being 2.2 x 10^–12.     

Beesioside III,a cyclolanostanol xyloside from the rhizomes of Beesia calthaefolia and Souliea vaginata

The chemical constituents of Beesia calthaefolia and Souliea vaginata were examined. From the rhizomes of B. calthaefolia, four new 9,19-cyclolanostanol xylosides, named beesiosides I–IV were isolated. Beesiosides 111 and IV were found also in the rhizomes of S. vaginata. On the basis of chemical and spectral evidence the structure of beesioside III was established as 15α-acetoxy-20ξ₁,24ξ₂-epoxy-9,19-cyclolanostane-3β,12β,16β,25-tetraol-3-O-β-D-xylopyranoside.     

Dammarane saponins of leaves of Panax pseudo-ginseng subsp. himalaicus

From dried leaves of Panax pseudo-ginseng subsp. himalaicus collected in Eastern Himalaya, new dammarane saponins, named pseudo-ginsenosides-F₁₁ and -F₈ were isolated along with the known Ginseng-root saponins, ginsenosides-Rb₃, Rd and -Re. Pseudo-ginsenoside-F₈ was proved to be a mono-acetyl-ginsenoside-Rb₃ and the location of its acetyl group was established mainly by ¹³C NMR spectroscopy. Pseudo-ginsenoside-F₁₁, was identified as the 6-O-α-rhamnopyransyl(1 → 2)-β-glucopyranoside of 3β,6α,12β,25-tetrahydoxy-(20S,24R)-epoxy-dammarane. The C-24 configuration of ocotillone and its related triterpenes was confirmed to be 24R excluding the recent comment by Lavie et al.     

Dinitrogen fixation in male-sterile soybeans

Partial male-sterile (ms₄/ms₄) soybeans (Glycine max L. Merr.) and their fertile isoline (Ms₄/Ms₄) were grown in adjoining field plots. From 62 until 92 days after emergence, the nitrogenase activity, assayed by acetylene reduction, of the average male-sterile plant was approximately twice that of the average fertile plant. At approximately 100 days after emergence, the assayable nitrogenase activity of the fertile plants fell to zero, whereas the nitrogenase of the partial male-sterile plants continued to be active for two additional weeks. Thus, this male-sterile plant seems to fix dinitrogen both at a higher rate and over a longer duration than does its fertile isoline.     

Skin irritant diterpene orthoesters of the daphnane type from Peddiea africana and P. Volkensii

From roots of Peddiea volkensii (Thymelaeaceae) the irritant factors V₁ and V₂ and from roots of P. africana the irritant factor A₁ were isolated. Their structures are the 9,13,14-ortho-(2,4,6-decatrienoates) of 5β-hydroxyresiniferonol-6α,7α-oxide (V₁) and of 5β,12β-dihydroxyresiniferonol-6α,7α-oxide (A₁) and the 12-O-acetate of the latter (V₂). Factors V₁ and V₂ do not exhibit tumour-promoting activity in the standard initiation-promotion protocol on mouse skin, although V₁ is a moderate irritant.     

Influence of CH3 group of μ-N-C-S ligand on the properties of [Fe2(C4H5N2S)2(NO)4] complex

Bi-nuclear neutral sulfur-nitrosyl iron complex [Fe₂(SR)₂(NO)₄] (I) has been obtained by replacement of thiosulfate ligands in dianion [Fe₂(S₂O₃)₂(NO)₄]²⁻ by 1-methyl-imidazole-2-yl. From X-ray analysis data, the complex has centrosymmetrical dimeric structure, with the iron atoms being linked via μ-N-C-S bridge. From Mossbauer spectroscopy, isomeric shift δ_Fe is 0.180(1) mm/s and quadrupole splitting ΔE_Q is 0.928(2) mm/s at T = 290 K. By comparative studying the mass-spectra in the gaseous phase of solid samples decomposition and kinetics of NO release in 1% aqueous solutions of dimethylsulfoxide, using of the ligand with CH₃ substituent in position 1 of imidazole-2-thiol was shown to yield a more stable donor of nitrogen monoxide than earlier obtained analog with imidazole-2-thiol, [Fe₂(C₃H₃N₂S)₂(NO)₄].     

Lanostane triterpenes of Canscora decussata

From the aerial parts of Canscora decussata Schult (Gentianaceae), five triterpenes, viz. gluanone, canscoradione, friedelin, fridelan-3-β-ol, and β-amyrin, three sterols, viz. sitosterol, stigmasterol, and campesterol, besides liberal amount of a mixtures of n-alkanes (C₂₇-C₃₁) and n-alkanols (C₂₆-C₃₂) have been isolated. The identity of the compounds has been established by chemical transformations, spectral evidence, and by direct comparison, where possible, with authentic reference materials. Gluanone and canscoradione have not been encountered before in nature.     

Structure characterization of haemostatic diosgenin glycosides from paris polyphylia

From Paris polyphylla var. chinensis Hare (Liliaceae), four diosgenin glycosides with haemostatic effects were isolated. The structure of the major component was elucidated by chemical and spectroscopic methods as 3-{[α-L-rhamnopyranosyl(1_Rha → 2_Glu)]-[α-L-arabinofuranosyl(1_Ara → 4_Glu)]-β D-glucopyranosyl}-25(R)-spirost-5-en-3β-ol. This saponin was found to be identical to three previously reported compounds to which other structures were originally assigned, namely the major component from P. polyphylla Smith, the major cytotoxic component of yunnan paiyao, and polyphyllin D from P. polyphylla grown in the Himalaya region.     

Light-Dependent Oxygen Uptake, Glycolate, and Ammonia Release in l-Methionine Sulfoximine-Treated Chlamydomonas

Glycolate and ammonia excretion plus oxygen exchanges were measured in the light in l-methionine-dl-sulfoximine treated air-grown Chlamydomonas reinhardii. At saturating CO₂ (between 600 and 700 microliters per liter CO₂) neither glycolate nor ammonia were excreted, whereas at the CO₂ compensation concentration (<10 microliters per liter CO₂) treated algae excreted both glycolate and ammonia at rates of 37 and 59 nanomoles per minute per milligram chlorophyll, respectively. From the excretion values we calculate the amount of O₂ consumed through the glycolate pathway. The calculated value was not significantly different from the component of O₂ uptake sensitive to CO₂ obtained from the difference between O₂ uptake of the CO₂ compensation point and at saturating CO₂. This component was about 40% of stationary O₂ uptake measured at the CO₂ compensation point. From these data we conclude that glyoxylate decarboxylation in air-grown Chlamydomonas represents a minor pathway of metabolism even in conditions where amino donors are deficient and that processes other than glycolate pathway are responsible for the O₂ uptake insensitive to CO₂.     

Cyanide bridged trinuclear complexes with central metals bearing pyridine ring ligands

Starting from Fe, Mn, Co and Ni precursors with Py, Bpy and Phen ligands 31 new trinuclear cyanide bridged complexes were obtained, in which the units (CO)₅Cr-CN, (CO)₅Mo-CN, (CO)₅W-CN, Cp(CO)₂Fe-CN, Cp(dppe)Fe-CN and Cp(PPh₃)₂Ru-CN occupy the external positions. Structure determinations showed that the central metals display cis- and trans-octahedral as well as tetrahedral ML_n(NC-M^′)₂ coordinations. From the ν(CN) bands in the IR spectra and from the redox potentials of the external organometallic units it can be concluded that the central complex units are electron sinks. This property prevents electronic communication between the two external metal centers.     

Changes in stomatal characteristics and photochemical efficiency during leaf development in six species of Sorbus

Measurements of Sorbus stomata size and density, maximal photochemical efficiency of photosystem II (F_v/F_m), variable-to-initial fluorescence ratio (F_v/F₀) and potential electron acceptor capacity (‘area’) were performed during leaf development in four parental diploid species, S. aria, S. aucuparia, S. chamaemespilus, S. torminalis, and two hybrid species, S. hazslinszkyana and S. intermedia. In fully expanded mature leaves, stomata lengths and densities were significantly larger in the shrub S. chamaemespilus than in the five tree species. The best performance of both the F_v/F_m and the F_v/F₀ ratio was recorded in S. intermedia, whereas S. chamaemespilus had the highest value of ‘area’. From a physiological point of view, the results of this study showed that the photosystem II reaction centers remained intact functionally through all phenological stages of leaf expansion for all examined species of Sorbus.     

Structures of some botryococcenes: branched hydrocarbons from the b-race of the green alga Botryococcus braunii

Nine branched hydrocarbons of the botryococcene type (C_nH_2n-10 30 ? n ? 37) have been isolated from the green alga Botryococcus braunii. Hydrocarbon mixtures were recovered from wild algae collected in fresh water lakes or from the same strains growing in laboratory; they were further separated by reversed-phase, and in some cases by normal phase, HPLC. From chemical investigations, GC/MS analyses, ¹H and ¹³C NMR spectroscopy, the structures of four new botryococcenes (one C₃₃H₅₆, two C₃₄H₅₈ and one C₃₇H₆₄) were elucidated.     

A diterpene from Euphorbia maddeni

From the anticancer-active CHCl₃, extract of the plant Euphorbia maddeni, a polyacylated diterpene of jatrophone type, euphornin, has been isolated and its structure elucidated by physico-chemical methods.     

Estimation of Growth Rate from the Mitotic Index

The growth rate of a eukaryotic population dividing at a constant rate can be estimated from the equation, t_m/g ln 2 = ln (1 + R), in which t_m is the time required for mitosis, g is the generation time, and R is the fraction of cells undergoing mitosis. Values for t_m and R can be determined by direct microscope examination of the population. The validity of the derived equation has been checked with an exponentially growing culture of a prokaryote, Escherichia coli, in which chloramphenicol was administered to inhibit protein synthesis. Cells having enough protein completed the division process whereas the rest of the population was inhibited. From the plot of the growth curve before and after administration of chloramphenicol, t_m and R were estimated. The calculated and actual growth rates were almost identical.