3-Amino­carbonyl­pyridinium difluoro­acetate at 123 K

In the crystal of the title compound, C6H7N2O+·C2HF2O2 −, the cation adopts a catemeric N—H⋯O hydrogen-bonded chain motif involving the carboxamide group, with two further N—H⋯O hydrogen bonds connecting the cations to adjacent difluoro­acetate anions via the carboxamide and pyridinium N atoms. The carboxamide group of the nicotinamidium ion is twisted by 32.3 (6)° from the pyridine ring plane. A number of C—H⋯O and C—H⋯F interactions consolidate the packing

Structure and stability of two polymorphs of creatine and its monohydrate

An experimental search for crystalline forms of creatine including a variable temperature X-ray powder diffraction study has produced three polymorphs and a formic acid solvate. The crystal structures of creatine forms I and II were determined from X-ray powder diffraction data plus the creatine formic acid (1 : 1) solvate structure was obtained by single crystal X-ray diffraction methods. Evidence of a third polymorphic form of creatine obtained by rapid desolvation of creatine monohydrate is also presented. The results highlight the role of automated parallel crystallisation, slurry experiments and VT-XRPD as powerful techniques for effective physical form screening. They also highlight the importance of various complementary analytical techniques in structural characterisation and in achieving better understanding of the relationship between various solid-state forms. The structural relationships between various solid-state forms of creatine using the XPac method provided a rationale for the different relative stabilities of forms I and II of creatine with respect to the monohydrate form

Nicotinamide–2,2,2-trifluoro­ethanol (2/1)

The nicotinamide (NA) mol­ecules of the title compound, 2C6H6N2O·C2H3F3O, form centrosymmetric R 2 2(8) hydrogen-bonded dimers via N—H⋯O contacts. The asymmetric unit contains two mol­ecules of NA and one trifluoroethanol molecule disordered over two sites of equal occupancy. The packing consists of alternating layers of nicotinamide dimers and disordered 2,2,2-trifluoro­ethanol mol­ecules stacking in the c-axis direction. Intra­molecular C—H⋯O and inter­molecular N—H⋯N, O—H⋯N, C—H⋯N, C—H⋯O and C—H⋯F inter­actions are present

Oscillatory Dynamics of Cell Cycle Proteins in Single Yeast Cells Analyzed by Imaging Cytometry

Progression through the cell division cycle is orchestrated by a complex network of interacting genes and proteins. Some of these proteins are known to fluctuate periodically during the cell cycle, but a systematic study of the fluctuations of a broad sample of cell-cycle proteins has not been made until now. Using time-lapse fluorescence microscopy, we profiled 16 strains of budding yeast, each containing GFP fused to a single gene involved in cell cycle regulation. The dynamics of protein abundance and localization were characterized by extracting the amplitude, period, and other indicators from a series of images. Oscillations of protein abundance could clearly be identified for Cdc15, Clb2, Cln1, Cln2, Mcm1, Net1, Sic1, and Whi5. The period of oscillation of the fluorescently tagged proteins is generally in good agreement with the inter-bud time. The very strong oscillations of Net1 and Mcm1 expression are remarkable since little is known about the temporal expression of these genes. By collecting data from large samples of single cells, we quantified some aspects of cell-to-cell variability due presumably to intrinsic and extrinsic noise affecting the cell cycle

Combined experimental and theoretical studies of intermolecular interactions in crystalline solids

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

An O2 smart plastic film for packaging

The preparation and characterisation of a novel, water-proof, irreversible, reusable, UV-activated, O2 sensitive, smart plastic film is described. A pigment, consisting of a redox dye, methylene blue (MB), and a sacrificial electron donor, DL-threitol, coated onto an inorganic support with semiconductor functionality, TiO2, has been extruded in low-density polyethylene (LDPE). The blue-coloured indicator is readily photobleached in <90 s using UVA light (4 mWcm−2), whereby MB is converted to its colourless, leuco form, leuco-methylene blue (LMB). This form persists in the absence of oxygen, but is re-oxidised to MB in 2.5 days in air under ambient conditions (21°C, 65% RH) within the O2 smart plastic film. The rate of recovery is linearly dependent upon the ambient level of O2. At the lower temperature of 5°C, the kinetics of the photobleaching activation step is largely unchanged, whereas that of recovery is markedly reduced to t1/2 = 36 h at 5°C (cf. 9 h at 21°C); the activation energy for the recovery step was calculated as 28 kJmol−1. The O2-sensitive recovery step was found to be moderately dependent upon humidity at 21°C, but not significantly dependent upon humidity at 5°C. The possible application of this type of indicator in food packaging is illustrated and discussed briefly

Experimental and predicted crystal energy landscapes of chlorothiazide

An experimental search for physical forms of the thiazide diuretic compound chlorothiazide comprising 402 different crystallizations identified one nonsolvated form and ten crystalline solvates. There are five distinct conformations in the experimental crystal structures which are in good agreement with the conformational minima found by ab initio optimization of the isolated molecule structure. An approximate rigid-body crystal energy landscape using these five conformations produced a diverse range of low energy crystal structures, with the anhydrous structure among the most stable. Inspection of the molecular packing adopted in both the experimental and predicted structures highlighted a number of chlorothiazide···chlorothiazide motifs that result from packing the different conformers. Specifically, four bimolecular face-to-face motifs were observed in most of the predicted structures and all of the experimental structures. The role of these robust intermolecular packing motifs and of the organic solvent molecules in stabilizing the experimental solvate structures of chlorothiazide is discussed. The results highlight the value of the approximate crystal energy landscape for flexible organic molecules in assisting with the interpretation of solid-state diversity in chlorothiazide crystal structures and identifying key stabilizing packing features

Assessing the long-term evolution of water supply capacity : comparison of two Mediterranean catchments

International audienceThis study aims at defining the main stakes in the development of a generic, multidisciplinary approach to evaluate water supply capacity and its spatial and temporal variability over long time periods. A common modelling framework was applied over two Mediterranean basins with different physical and anthropogenic characteristics: the Ebro (85 000 km2, Spain) and the Hérault (2500 km2, France) catchments. Runoff and river flow regulations were simulated using conceptual hydrological models and reservoir management models, respectively. Water demand was estimated from population and unit water consumption data for the domestic sector, and from irrigated area, crop, soil and climatic data for theagricultural sector. A ratio comparing water resource availability to water demand was computed on each catchment. Working on two catchments with different geographical scales and water management issues underlines the challenges in the development of a reliable and generic water allocation assessment method

Carbamazepine trifluoroacetic acid solvate

Carbamazepine forms a 1:1 solvate with trifluoroacetic acid (systematic name: 5H-dibenzo[b,f] azepine-5-carboxamide trifluoroacetic acid solvate), C(15)H(12)N(2)O center dot C(2)HF(3)O(2). The compound crystallizes with one molecule of carbamazepine and one of trifluoroacetic acid in the asymmetric unit to form an R(2)(2)(8) motif. The solvent molecule is disordered over two sites, with site-occupancy factors 0.53 (1) and 0.47 (1)