F.J. Martin-Gil

Evidence of a low compressibility carbon nitride with defect-zincblende structure

A carbon-nitride compound with defect zincblende structure (P43m) has been discovered in samples prepared by a chemical precursor route. Crystallographical (high-resolution electron microscopy and electron nanodiffraction) and electron energy loss measurements has been performed to identify the material as cubic zincblende with C3N4 composition. Nanoindentation indicates a high elastic recovery and hardness. The results agree with detailed ab initio calculations on metastable structures and compressibility. Our synthesis method is projected to be a process that could produce large quantities of material by controlling the chemical strategy. The new compound has potential applications for high hardness, elasticity and thermal conductivity materials and thin films.

DTG and dta studies on typical sugars

Abstract The DTG and DSC-DTA techniques have been found to be suitable for the investigation of typical sugars between 25°C and 700°C. Endothermic and exothermic reaction temperatures and enthalpies of 24 sugars are listed. These data serve not merely to characterize or identify substances, but to yield important information pertaining to the relation between molecular structure and thermal behaviour.

Differential scanning calorimetry investigations on LPS and free lipids A of the bacterial cell wall

Differential scanning calorimetry (DSC) was used to investigate the thermal stability and behaviour of the lipopolysaccharides (LPS) of the outer membrane of Gram-negative bacteria and their lipid portion. DSC curves of LPS show thermal features between 200 and 129 degrees C (depolymerization) and between -13 and -36 degrees C (cooling phase transition). Both effects were related to the relative strength of the linkage types in the O-chain structure and to their capacity for intermolecular hydrogen bonding. DSC curves of lipids A show endotherm peaks between 40 and 24 degrees C, around 15 degrees C and between -23 and -4 degrees C. Based on these effects, strong differences in thermal behaviour can be observed between that of Brucella and Vibrio cholerae on the one hand, and that of Escherichia coli and Shigella flexneri on the other. Fluidity of the acyl chains and lyotropism, which are important parameters in expression of biological activities, are discussed using the above data. To explain some properties, fluidity could be related to the temperature of the gel<==>liquid crystalline (beta<==>alpha) phase transition, which occurs at physiological temperature. Nevertheless, fluidity could be related to temperature of the previous thermal effect (between 6 and 20 degrees C), for which a softening or partial melting of the sample has been evidenced. The thermal effect measured between -23 degrees C and -4 degrees C indicates a greatly reduced water concentration of lipid A from Brucella, thus explaining its early fusion process and its activity by means of hydrophobic interactions.

Hepatitis C virus genotype 4 in a North-west Spain district

Hepatitis C virus (HCV) genotype 4 has been reported to be the most prevalent genotype in Central Africa, the Middle East, and Egypt but not in Western countries (Alfonso et al., 2001). Recently, seven genotype 4 isolates were detected in Canary Islands (Martin et al., 1998). Also surprisingly, an unexpected high prevalence of genotype 4 in both North-east (Fuster et al., 2002) and Southern Continental Spain have been reported (Sanchez-Quijano et al., 1997). To supplement the map of distribution of HCV genotype 4 in Spain we would like to report the data of patients from the North-west-Centre of the Iberian Peninsula, attended in our hospital. HCV genotypes were determined by reverse hybridisation line probe assay with the INNOLiPA HCV II test (Innogenetics, Brussels, Belgium) on RT-PCR products generated from Amplicor kit (Roche Diagnostics). Serum HCV RNA levels were quantified by RT-PCR with the HCV Monitor quantitative assay (Roche Diagn. Sys. Branchburg, NJ, USA). All commercial tests were used according to the manufacturers’ instructions. In addition, for a few selected samples, the HCV TruGene 5? NC assay (Visible Genetics) a CLIPTM sequencing method, has been applied. Between June 1999 and July 2002, HCV isolates were genotyped at our laboratory. The prevalence of HCV genotypes is shown in Table 1. We found a high percentage of the genotype 4 among the collected samples*/in 26 (7%) out of 355 cases. The mean age of HCV genotype 4-harboring patients was 39 years, with a high prevalence (71%) of men. LIPA subtype analysis into genotype 4 was as follows: four indeterminate: five isolates (23.8%), subtype 4c/4d: 16 (61.5%), and subtype 4f: 1 (3.8%). The subtype 4f was observed in a sample from a 77-year-old man. TruGene assay has allowed us to subtype as 4a two out of these nine LIPA un-subtyped genotype 4 samples, and to confirm as 4c one doubtful 4c/4d sample. An analysis of the distributions mentioned above shows that although the predominant type was type 1, the high prevalence of genotype 4 accompanied by a high percentage of genotype 3, more frequent in intravenous drug users (IVDU) patients (Harzic et al., 2001), deserves special attention to this route of infection. Patient questioning and data base revision determined that 10 of 26 HCV genotype 4harboring individuals were IVDU and HIV-infected. Thus, three 4-indeterminate genotyped * Corresponding author. Journal of Clinical Virology 28 (2003) 223 /224

Low temperature thermal behaviour of chitins and chitin—glucans

Abstract In chitin, chitin—glucans and some chitosans, cooling to temperatures between −13 and −31°C apparently reduces or breaks linkages between the sheets of chains in their structures. When additionally an alkaline medium of NaOH, KOH or LiCl/amide exists, this tendency to break is strengthened, reaching in all cases solvation and subsequent dissolution. In chitin, the solubilized fractions correspond to the crystalline β-form or to amorphous materials. In chitin—glucans, the solubilized fraction is a disorganized material in which the chitin remains firmly bound to glucan. In a DSC study, the thermal effect that appears at around −22°C is derived from the phase transition between the distorted structure poor in intersheet hydrogen bonding and the undistorted structure rich in intersheet bonding. In chitin, it seems that the phase transition occurs from the β- to the α-form, although a change from a bent to a straightened configuration could also explain it.

Thermal studies on sulphonamide derivative complexes: Part 1. Thermal behaviour of acetazolamide-Copper complexes

Abstract The thermal behaviour of the complexes CuAcm(NH 3 ) 3 , CuAcm(NH 3 ) 2 ·2H 2 O, 2 CuAcm(NH 3 )·H 2 O and Cu 3 Acm(OH) 4 ·3H 2 O has been studied by TG and, DTA techniques in flowing air and nitrogen atmospheres as well as by IR spectroscopy. The complexes decompose in two steps: (a) dehydration and/or deammination and (b) pyrolytic decomposition to copper oxides and copper sulphides. The second step is accompanied by an increase in mass and a strong exothermic peak, attributed to the oxidation of copper sulphides to cupric sulphate. Obviously, this oxidation process does not take place in a nitrogen atmosphere.

Crystal structures and thermal decomposition oftrans-Pd(Creat)2Cl2·2H2O andcis-Pt(Creat)2I2·3H2O

New complexes of the formulaetrans-Pd(Creat)2Cl2·2H2O (I) andcis-Pt(Creat)2I2·3H2O (II) have been prepared and their structures and stabilities studied by X-ray diffraction and thermal analysis. Both compounds have a squareplanar geometry, the two Cl atoms and N1 creatinine atoms are coordinated to Pd intrans configuration, while in compoundII the I atoms and N1 atoms are coordinated incis configuration. In spite of the earlier differences, the TG and DTA curves of the complexes show that their stability is very similar. Since an extended hydrogen bond system is present in the crystals, especially inII, the possible consequences in biological media are discussed briefly.ZusammenfassungEs wurden neue Komplexe der Formelntrans-Pd(Creat)2Cl2·2H2O (I) undcis-Pt(Creat)2I2·3H2O (II) hergestellt und ihre Strukturen und Stabilitäten mittels Röntgenstrukturanalyse bzw, thermischer Analyse untersucht. Beide Komplexe haben quadratisch-planare Struktur, die zwei Cl-Atome und die N1-Creatinin-Atome sind an Pd intrans-Konfiguration koordiniert, währenddessen in VerbindungII die I-Atome und die N1-Atome incis-Konfiguration zueinander stehen. Trotz früherer Differenzen zeigen die TG- und DTA-Kurven der Komplexe, daß ihre Stabilitäten sehr ähnlich sind. Da besonders inII ein ausgedehntes Wasserstoffbindungssystem vorhanden ist, werden auch mögliche Konsequenzen bezüglich biologischer Wirksamkeit kurz diskutiert.

Water of hydration and cross-linking in live and dead cells

Abstract Thermal analysis has been used successfully for the in vitro estimation of aging-related changes in biological materials, such as human erythrocytes and spermatozoa, human ear cartilage and porcine scleral tissue cells. Through low-temperature DSC curves we have observed that, as a cellular population ages, the glass-transition temperature of the overall cellular constituents (−31°> T g >−50°C) shifts to higher values. Conversely, the usual procedures followed in cryobiology to improve cellular survival (i.e. procedures that use rapid freezing by vitrification in a sugar medium, like sucrose, glycerol and PPG, to reduce the amount of freezable water in the live cells) shift the T g to lower temperatures. Thus, T g has been shown to be a very good marker in the control of the in vitro vitality degree of a cellular population. Statistically, the cellular life-to-death curves, both for erythrocytes and spermatozoa, can be described by a cubic model.

Metallography of ancient bronzes: Study of pre-roman metal technology in the Iberian Peninsula

Abstract The metallographic examination of 26 bronze archaelogical objects is discussed together with the routine developed for this. The main aim was to define the bronze technology known by the Vaccei (a Celtiberian culture from Spain). All of the objects studied here come from cremation graves and their chronologies cover the last five centuries BC. The older objects have reflected great skill in forging, which compensated for casting problems. These casting problems decreased gradually, but were still important until the Roman conquest, when a real advance in casting techniques can be recorded. Since we were not authorized to cut or mount the objects in plastic, we had to hold them in our bare hands and polish only their outer surfaces, which caused many scratches and other marks. This report also illustrates some of the technical problems that might arise when studying archaeological materials.

Thermal analysis of lipopolysaccharides from Brucella and other Gram-negative bacteria

Abstract DSC curves of chromatographically purified lipopolysaccharides (LPS) of Gram-negative bacteria show very similar thermal features between (I) Brucella melitensis and Salmonella typhimurium; between (II) Salmonella enteritidis and Pseudomonas aeruginosa ; and among (III) Escherichia coli, Shigella flexneri and Serratia marcescens . The order of thermal stabilities is III > II > I, in agreement with results previously obtained from the whole bacteria. The established relative strength for linkage types (1 → 3) > (1 → 6) > (1 → 4) > (1 → 2) has been useful to justify the thermal lability of Brucella abortus (with only (1 → 2) linkages in its O-chain) and Brucella melitensis (one (1 → 3) and four (1 → 2) linkages) versus other Gram-negative bacteria (with O-chains rich in β/β-(1 → 3), α/β-(1 → 4) or α-(1 → 6) linkages).