Structural Chemistry 

About: Structural Chemistry is an academic journal published by Springer Science+Business Media. The journal publishes majorly in the area(s): Molecule & Hydrogen bond. It has an ISSN identifier of 1040-0400. Over the lifetime, 3991 publications have been published receiving 40719 citations.

Pectin, a versatile polysaccharide present in plant cell walls

Abstract: Pectin or pectic substances are collective names for a group of closely associated polysaccharides present in plant cell walls where they contribute to complex physiological processes like cell growth and cell differentiation and so determine the integrity and rigidity of plant tissue. They also play an important role in the defence mechanisms against plant pathogens and wounding. As constituents of plant cell walls and due to their anionic nature, pectic polysaccharides are considered to be involved in the regulation of ion transport, the porosity of the walls and in this way in the control of the permeability of the walls for enzymes. They also determine the water holding capacity. The amount and composition of pectic molecules in fruits and vegetables and other plant produce strongly determine quality parameters of fresh and processed food products. Pectin is also extracted from suitable agro-by-products like citrus peel and apple pomace and used in the food industry as natural ingredients for their gelling, thickening, and stabilizing properties. Some pectins gain more and more interest for their health modulating activities. Endogenous as well as exogenous enzymes play an important role in determining the pectic structures present in plant tissue, food products, or ingredients at a given time. In this paper functional and structural characteristics of pectin are described with special emphasis on the structural elements making up the pectin molecule, their interconnections and present models which envisage the accommodation of all structural elements in a macromolecule. Attention is also given to analytical methods to study the pectin structure including the use of enzymes as analytical tools.

Nanocluster analysis of intermetallic structures with the program package TOPOS

Abstract: General principles of the analysis of intermetallic compounds with the program package TOPOS are considered. The nanocluster method is described in detail, which lies in the base of the TOPOS “Nanoclustering” procedure. The applications of the nanocluster method to intermetallic compounds as well as to porous materials are comprehensively overviewed. The perspectives of extending the nanocluster model to other classes of inorganic compounds are outlined.

Heat capacity corrections to a standard state: a comparison of new and some literature methods for organic liquids and solids

Abstract: The estimation methods commonly used to correct phase change enthalpies to the standard state are compared where possible to experimental measurements. Heat capacity corrections for liquid-gas equilibria are found to correlate with molecular structure, and we suggest an improved method for estimating these corrections using group methods. A similar improvement for estimating heat capacity corrections for solid-gas equilibria using group methods is also proposed. Heat capacity corrections for liquid-solid equilibria are examined. These corrections were found to be comparable in magnitude to the experimental error associated with heat capacity measurements, so it was not possible to obtain any meaningful correlations.

Wavefunction and reactivity study of benzo[a]pyrene diol epoxide and its enantiomeric forms

Abstract: Benzo[a]pyrene is a known carcinogen, which derives from fossil fuel combustion, cigarette smoke, and generic biomass combustion including traffic emissions. This potent carcinogen has a well-known mechanism of action, leading to the formation of adducts with the DNA, primarily at guanosine positions. The reactivity and chemistry of this notorious compound are, however, dependent on the electronic configuration of the biologically activated metabolite, the benzo[a]pyrene diol epoxide. The activated metabolite exists mainly as four isomers, which have particular chemical reactivities toward guanosine sites on the DNA. These isomers exert also a different carcinogenicity compared to one another, which is a feature that is conventionally attributed to their geometry. However, the reactivity and properties of the isomers are not fully defined, and a determination of these properties by wavefunction behavior is required. This study reports the electronic properties of the benzo[a]pyrene diol epoxide enantiomers, along with a detailed analysis of the energy landscape, geometry, and electronic configuration of the epoxide ring. The results show that the epoxide ring, the core of the reactivity, bears different properties at the level of wavefunction for each isomer. Each of the isomers has a distinct profile on the epoxide ring, in terms of hydrogen bonds and in terms of the non-covalent interaction between the diol groups and the epoxide. These profiles generate differential reactivities of epoxide group, which can be attributed to its local bond lengths, the electron localization function, and polarized bonds. Most interestingly, the quantum chemical calculations showed also that the epoxide ring is inclined more perpendicularly toward the angular ring plane for the more carcinogenic isomers, a feature which suggests a potential geometrical relationship between the inclination of the epoxide group and its interaction with the guanosine group upon adduct formation. Our results introduce novel and crucial information, which assist in understanding the mechanism of toxic potential of this known molecule, and display the strength and level of detail of applying quantum chemical methods to reveal the reactivity, energy properties, and electronic properties of a mutagen.

A group additivity approach for the estimation of heat capacities of organic liquids and solids at 298 K

Abstract: A group additivity method is described which provides heat capacity estimates of the condensed phase. The data base consists of 810 liquids and 446 solids. Group values for carbon in various common substitution and hybridization states and for 47 functional groups are provided. The standard error of estimation using this approach on this data base is 19.5 (liquids) and 26.9 J/ (mole K) (solids). This can be compared to typical experimental uncertainties of 8.12 and 23,4 J/ (mole K) associated with these measurements, respectively. Experimental uncertainties were estimated from the numerical differences obtained for a given substance from multiple independent literature reports.