Existence Of Microheterogeneity Research Articles

Parameters of the Microheterogeneous Structure of Liquid 110G13L Steel

Original experimental data on the viscosity, density, surface tension, and electrical resistivity of liquid 110G13L steel are presented. The results from measurements are discussed in terms of the concepts of the microheterogeneity of metal melts. The relationship between the structure-sensitive properties of metal melts—viscosity, density, surface tension, and electrical resistance—is studied in the context of exploring the conditions for the existence of microheterogeneity. Based on experimental data, a conclusion is drawn about the laws governing the evolution of microheterogeneity upon a change in the temperature of a melt, and a numerical estimate is made of the parameters of the microheterogeneous structure of the liquid steel, particularly the sizes of dispersed particles.

Mixed Macromolecular Crowding: A Protein and Solvent Perspective.

In the living cell, biomolecules perform their respective functions in the presence of not only one type of macromolecules but rather in the presence of various macromolecules with different shapes and sizes. In this study, we have investigated the effects of five single macromolecular crowding agents, Dextran 6, Dextran 40, Dextran 70, Ficoll 70, and PEG 8000 and their binary mixtures on the modulation in the domain separation of human serum albumin using a Förster resonance energy transfer-based approach and the translational mobility of a small fluorescent probe fluorescein isothiocyanate (FITC) using fluorescence correlation spectroscopy (FCS). Our observations suggest that mixed crowding induces greater cooperativity in the domain movement as compared to the components of the mixtures. Thermodynamic analyses of the same provide evidence of crossovers from enthalpy-based interactions to effects dominated by hard-sphere potential. When compared with those obtained for individual crowders, both domain movements and FITC diffusion studies show significant deviations from ideality, with an ideal solution being considered to be that arising from the sum of the contributions of those obtained in the presence of individual crowding agents. Considering the fact that domain movements are local (on the order of a few angstroms) in nature while translational movements span much larger lengthscales, our results imply that the observed deviation from simple additivity exists at several possible levels or lengthscales in such mixtures. Moreover, the nature and the type of deviation not only depend on the identities of the components of the crowder mixtures but are also influenced by the particular face of the serum protein (either the domain I–II or the domain II–III face) that the crowders interact with, thus providing further insights into the possible existence of microheterogeneities in such solutions.

Short communication: Genetic variants of Sarcocystis cruzi in infected Malaysian cattle based on 18S rDNA

Sarcocystis species are pathogenic parasites that infect a wide range of animals, including cattle. A high prevalence of cattle sarcocystosis has been reported worldwide, but its status is unknown in Malaysia. This study focused on utilizing 18S rDNA to identify Sarcocystis species in Malaysian cattle and to determine their genetic variants. In this study, only Sarcocystis cruzi was detected in Malaysian cattle. The intra-species S. cruzi phylogenetic tree analysis and principal coordinate analysis (PCoA), respectively displayed two minor groups among the parasite isolates. This finding was supported by high Wright FST value (FST=0.647). The definitive hosts (dogs) may play a fundamental role in the development of S. cruzi genetic variants. Additionally, the existence of microheterogeneity within the S. cruzi merozoites and/or distinct genetic variants arisen from independent merozoites in mature sarcocysts, possibly contributed to the existence of intra-species variations within the population.

Viscosity and separation of Cu–Pb melts

Cu–Pb melts are studied by viscometry upon heating and subsequent cooling. The experimental results are used to plot the boundaries of the region of existence of microheterogeneities in the melts in the above-liquidus part of the Cu–Pb phase diagram.

Unraveling the heterogeneity in N butyl-N-methylpiperidinium trifluromethanesulfonimide ionic liquid by 1D and 2D NMR spectroscopy

Room temperature ionic liquids are one of the most exciting classes of materials in the last decade. In particular piperidinium (PIP) cation based ionic liquid (IL) (such as PIP14NTf2) have found application in electrochemistry/batteries. In this Letter, 2D NMR (NOESY and HOESY) is employed for studying the interactions present between cations and anions. HOESY spectrum shows that fluorine of NTf2 unusually interacts with all proton of the cation (PIP14). Combined HOESY and NOESY indicate that NTf2 anion is distributed heterogeneously in liquid. Existence of micro heterogeneity in this important class of IL is proposed.

Study on the microheterogeneity of aqueous alcohol solutions: formation mechanism of inner pores of ZnO nanostructures

The self-association of alcohols in water has been demonstrated by a number of special experiments and theoretical work. Here, we report a simple and effective method to investigate the presence of these hydrophobic aggregation areas. Porous ZnO nanostructures were prepared using a simple alcohol assisted solution synthetic method at room temperature. The presence of hydrophobic groups of alcohols resulted in the existence of microheterogeneities and organic aggregations in the mixed solution, which act as a soft template and play key roles in the formation of the porous structure of ZnO. A high reaction temperature resulted in decreased hydrogen bonding between the alcohol and water molecules, and increased hydrophobic interactions among the alcohol molecules as well as increased pore sizes of the ZnO nanostructures. Sphere-like and hexagonal pores were observed, which were a result of the in situ enwrapping of hydrophobic aggregation areas in alcohol aqueous solution.

Liquid Structure and Cluster Formation in Ionic Liquid/Water Mixtures – An Extensive ab initio Molecular Dynamics Study on 1-Ethyl-3-Methylimidazolium Acetate/Water Mixtures – Part

Abstract We present an extensive ab initio molecular dynamics study on mixtures of the room temperature ionic liquid 1-ethyl-3-methylimidazolium acetate with water. To show the dependence of the properties on the concentration, we simulated four different systems: Pure IL, pure water, and two binary mixtures with different mixing ratios. We found that the imidazolium rings are stacking on top of each other in the pure ionic liquid, which is a result of the strong dispersion interactions between the cations. With increasing water content, this ordering is disturbed. While in the pure IL the anions are located almost exclusively within the cation's ring plane, they occupy both the in-plane and the on-top position in the mixture. For very high water content, the anions are mainly found on top of the imidazolium ring. The ethyl chains of the cations attract each other via dispersion force and form clusters, indicating the existence of microheterogeneity in our simulations. We also analyzed the topology of the hydrogen bond network and found that the cation is forming hydrogen bonds to multiple anions at the same time, and is therefore a bridging agent. Likewise, the anion is bridging between different cations. At moderate water content, two acetate ions are frequently coordinated to the same water molecule, leading to the formation of acetate/water clusters.

PEG aggregation templated porous ZnO nanostructure: room temperature solution synthesis, pore formation mechanism, and their photoluminescence properties

Porous ZnO micro/nanostructures were prepared using a simple PEG assistant solution synthetic method at room temperature. The concentration of the zinc ions has a great influence on the morphology and chemical composition of the final products. The presence of hydrophobic groups of PEG resulted in the existence of microheterogeneities and the PEG aggregations in the mixed solution, which act as a soft template and play key roles in the formation of the porous structure of ZnO. High reaction temperature resulted in the decreased hydrogen bonding between the PEG and water molecules, and the increased hydrophobic interactions between the PEG chains as well as the increased pore size of final ZnO products. The influence of PEG molecular weight on the pore structure was also investigated. Photoluminescence studies show that the porous ZnO micro/nanostructures exhibited ultraviolet emission peak located at 385 nm and broad visible green emission peak centered at 525 nm with a shoulder at the yellow region. The origin and the intensity of the photoluminescence visible emissions was attributed to the structure defects, which was investigated by X-ray photoelectron spectroscopy.

Rheology of Concentrated Cellulose Solutions in 1-Butyl-3-methylimidazolium Chloride

Rheological behavior of the concentrated cellulose/1-butyl-3-methylimidazolium chloride ([BMIM]Cl) solutions was investigated. As polymeric fluid, solutions of cellulose in [BMIM]Cl display a marked elastic behavior under shear flow. The dependence of the shear viscosity η, and of the dynamic modulus, on concentration, average degree of polymerization (DP) and temperature is discussed. At lower concentrations and degrees of polymerization (DP), cellulose solutions show viscous, inelastic behavior at low frequencies and low shear rate. At higher concentration and DP, cellulose solutions are more elastic at higher frequencies and shear rate. Such solutions also have some usual rheological properties. The dynamic rheological responses revealed that the Cox–Merz rule did not hold for these cellulose solutions at high deformation rate. Plotting storage modulus G′ against loss modulus G″ gave almost a master curve which is independent of temperature and concentration, with the slope of about 1.651 for 10 wt% cellulose solutions. This value indicates the existence of microheterogeneity in the solution system.

Mass spectral evidence for N-glycans with branching on fucose in a molluscan hemocyanin

Glycopeptides, isolated from a trypsinolysate of functional unit (FU) RtH2- e of Rapana thomasiana hemocyanin subunit 2, were analysed by electrospray ionization mass spectrometry and MS/MS. From the molecular mass observed after deglycosylation, it was inferred that all glycopeptides shared the same peptide stretch 92–143 of FU RtH2- e with a glycosylation site at Asn-127. Besides the core structure Man 3GlcNAc 2 for N-glycosylation, structures with a supplementary GlcNAc linked to either the Man(α1–3) or the Man(α1–6) arm and/or an additional tetrasaccharide unit connected to the other Man arm were observed, indicating the existence of microheterogeneity at the glycan level. The tetrasaccharide unit contains a central fucose moiety substituted with 3- O-methylgalactose and N-acetylgalactosamine, and linked to GlcNAc at the reducing end. This structure represents a novel N-glycan motif and is likely to be immunogenic. A second potential site for N-glycosylation in FU RtH2- e at Asn-17 was shown to be not glycosylated.

The study of poly(styrene- co- p-(hexafluoro-2-hydroxylisopropyl)-α-methyl-styrene)/poly(propylene carbonate) blends by ESR spin probe and Raman

Different hydroxyl content poly(styrene- co- p-(hexafluoro-2-hydroxyisopropyl)-α-methylstyene) [PS(OH)] copolymers were synthesized and blends [noted for PP-X] with poly(propylene carbonate) [PPC] were prepared by casting from chloroform solution. The miscibility, micro heterogeneity and hydrogen bonding interaction of the component polymers were investigated by Differential Scanning Calorimetry (DSC), Electron Spin Resonance (ESR) spin probe method and Micro Raman spectroscopy. DSC results showed that the PP-2, PP-5, PP-8, PP-12 blends exhibited two distinct T gs, indicating immiscibility, while the PP-20 and PP-27 blends were miscible with the existence of a single T g. ESR results indicated that the probe molecule: Tempo couldn't give clear micro phase separation or miscibility information and thus was not sensitive to the investigated polymer blends system. On the contrary for all the blends spin probed with the probe molecules: Tempol and Tamine, two spectral components with different rates of motion: ‘fast’ and ‘slow’ motion were observed in different temperature range, which indicated the existence of micro heterogeneity on the molecular level; the more mobile PPC-rich micro phase and the more rigid PS(OH) rich micro phase. In addition, the scale of miscibility was progressively enhanced due to the increasing hydrogen bonding interaction between the hydroxyl in PS(OH) and the oxygen atoms in PPC. Meanwhile it was found that the degree of the probe molecule rotation detectable in the ESR spectrum was dependent on the polymer matrix rigidity and the strength of the hydrogen bonding between the probe molecule and the polymer matrix. Micro Raman substantiated the existence of the PS(OH)-rich micro phase and the PPC-rich micro phase. The hydrogen bonding strength between PS(OH) and PPC and the mixing level of the component polymers were increased gradually with the increase of hydroxyl content in the PS(OH) copolymer.

The study of poly(styrene-co-p-(hexafluoro-2-hydroxylisopropyl)-?-methylstyrene)/poly(ethylene oxide) blends

Different hydroxyl content poly(styrene-co-p-(hexafluoro-2-hydroxylisopropyl)-α-methylstyene) [PS(OH)-X] copolymers were synthesized and blends with 2,2,6,6-tetramrthyl-piperdine-1-oxyl end spin-labeled PEO [SLPEO] were prepared. The miscibility behavior of all the blends was predicted by comparing the critical miscible polymer–polymer interaction parameter (χcrit) with the polymer–polymer interaction parameter (χ). The micro heterogeneity, chain motion, and hydrogen bonding interaction of the blends were investigated by the ESR spin label method. Two spectral components with different rates of motion were observed in the ESR composite spectra of all the blends, indicating the existence of microheterogeneity at the molecular level. According to the variations of ESR spectral parameters Ta, Td, ΔT, T50G and τc, with the increasing hydroxyl content in blends, it was shown that the extent of miscibility was progressively enhanced due to the controllable hydrogen bonding interaction between the hydroxyl in PS(OH) and the ether oxygen in PEO. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2312–2317, 2004

Spin label study of phase morphology and polymer segmental motion in poly(acrylic acid)–poly(ethylene oxide) complex

AbstractThe ESR lineshapes of nitroxide radical end‐labeled on poly(ethylene oxide) (SLPEO) for the pure polymer and for different weight ratio complexes with poly(acrylic acid) (PAA) were studied as a function of temperature. For SLPEO one spectral component was detected in the entire temperature range, indicating that the spin label was in the homogeneous phase domain. For all PAA–PEO complexes two spectral components with different rates of motion, a ‘fast’ and a ‘slow’ component, were observed, which indicates the existence of microheterogeneity at the molecular level: the more mobile the PEO‐rich microphase, the more rigid is the PAA‐rich microphase. On the other hand, the SLPEO polymer segmental motion was restricted owing to the hydrogen bond interaction between the carboxyl proton in PAA and the ether oxygen in PEO. This restriction was exacerbated with increasing the PAA content in the complex, which could be further substantiated through the calculated S and τc values. Copyright © 2003 John Wiley & Sons, Ltd.

ＭＳによるＧＰＩアンカータンパク質の構造と機能の解析

The improved sensitivity and soft ionization characteristic of ESI-MS/MS and MALDI-TOF-MS were applied to the identification of characteristic fragment ions from C-terminal GPI-anchored peptides of bovine liver 5′-nucleotidase and other several GPI-anchored proteins. In the CID spectrum of ESI-MS/MS, characteristic fragment ions such as m/z 162 (glucosamine) and m/z 286 (mannose-phosphate-ethanolamine) were effectively identified. In matrix-assisted laser desorption/ionization (MALDI)-TOF-MS analysis, heterogeneous peaks of GPI-anchored peptides caused by sugar side chains were detected as single charged ions in positive mode analysis. In PSD analysis most of the expected product ions succeeding from the precursor GPI-anchored peptide were fully obtained. Thus ESI-MS/MS and PSD of MALDI-TOF-MS proved to be fairly effective in analyzing small amount of GPI-anchored structure less than 10 pmol. By LC-ESI-MS analysis, C-terminal peptides bearing the products of GPI were effectively detected by combination with in-source decay and multi-functional scanning for the several characteristic fragment ions from GPI-anchor structure. Existence of microheterogeneity was observed in the C-terminal GPI-anchored peptides from the 42 kDa and 40 kDa protein of bovine erythrocytes. By LC-ESI-MS, C-terminal GPI-anchor structure can be easily identified from the target protein even if its amino acid sequence data are not available.

Identification of a New Glycosylphosphatidylinositol-Anchored 42-kDa Protein and Its C-Terminal Peptides from Bovine Erythrocytes by Gas Chromatography–, Time-of-Flight–, and Electrospray-Ionization–Mass Spectrometry

By treatment with phosphatidylinositol-specific phospholipase C (PIPLC), we obtained several candidates of glycosylphosphatidylinositol (GPI)-anchored proteins such as 55, 42, 40, and 30 kDa from bovine erythrocyte membrane, in addition to the well-known GPI-anchored protein acetylcholinesterase. In these proteins, the presence ofmyo-inositol was confirmed by gas chromatography (GC)–mass spectrometry. Among them, the 42-kDa protein was further analyzed by electrospray-ionization (ESI)–mass spectrometry (MS) after hydrolysis by lysyl endoprotease. By liquid chromatography (LC)–ESI–MS analysis, C-terminal peptides bearing the products of GPI (Ct. GPI-peptides) were effectively detected by combination with in-source collision and multifunctional scanning for the several characteristic fragment ions from the GPI-anchor structure. Existence of microheterogeneity was also observed in the Ct. GPI-peptides from the 42-kDa protein. This result was confirmed by analysis with time-of-flight (TOF)–MS. Furthermore, one of the Ct. GPI-peptides was analyzed in ESI–MS–MS mode. Characteristic fragment ions were effectively detected by collision-induced decay. By the result of MS–MS analysis, this GPI-anchor structure was revealed to contain additionalN-acetyl hexosamine. By the above-mentioned method, the C-terminal GPI-anchor structure can be easily identified from the target protein even if its amino acid sequence data are not available.

Stability and instability properties of aggregation of single chain amphiphiles into binary mixtures

In a lysophospholipid binary mixture, there are three ways of association between the mixture components of single-chain amphiphiles: (a) between two identical molecules each of the first and second component (self-association process) and (b) between two different molecules (cross-association process). Association probabilities for three binary mixtures were analysed as functions depending on the electric dipole moments of the polar head groups. A 3-D view representation is most suitable for this analysis. The most important finding is that for certain values of the electric dipole moments there are molecular couples which have a maximum stability to the changes in the external electrolytic medium. This fact confirms the formation of clusters and their stability, which is equivalent to the existence of micro-heterogeneities within the lipid bilayers. On the other hand, there are unstable molecular associations, and this fact influences the appearance of some phase transitions. Generally, the increase of the electric dipole moment or the increase of the acyl-chain length of one component from a binary lipid mixture decreases the self-association probability between its own molecules, but it increases the self-association probability of the other mixture components. Furthermore, the cross-association probability has high values for any binary lipid mixture of single-chain amphiphiles.

Nonlinear optical studies of binary mixtures of hydrogen bonded liquids.

We applied two nonlinear optical techniques for investigating ${\mathrm{CH}}_{3}$OH-${\mathrm{H}}_{2}$O and ${\mathrm{CH}}_{3}$CN-${\mathrm{H}}_{2}$O binary liquid mixtures. The measured third-harmonic susceptibility of ${\mathrm{CH}}_{3}$OH-${\mathrm{H}}_{2}$O with varying methanol mole fraction sensitively reflects the microstructure of the liquids. The perturbed polar distribution of methanol molecules by interfacial water at the vapor-liquid interface of ${\mathrm{CH}}_{3}$OH-${\mathrm{H}}_{2}$O was revealed with infrared-visible sum-frequency generation (IVSFG). For ${\mathrm{CH}}_{3}$CN-${\mathrm{H}}_{2}$O our third-harmonic-generation result clearly indicates the existence of microheterogeneity in a mixture with a mole fraction of acetonitrile larger than 0.3. By comparing with an IVSFG study of ${\mathrm{CH}}_{3}$CN-${\mathrm{H}}_{2}$O reported by Eisenthal et al. [J. Chem. Phys. 98, 5099 (1993)], the observed critical acetonitrile concentration for the onset of phase separation in ${\mathrm{CH}}_{3}$CN-${\mathrm{H}}_{2}$O appears to be larger than that at the liquid surface.

Characterization of glycoproteins: carbohydrate structures of glycoprotein hormones.

Gylcoproteins are a complex group of macromolecules that are widely distributed in nature. They are present virtually in all forms of life and are involved in important biological functions (Wagh and Bahl, 1981; Sharon and Liz, 1982; Kobata, 1984). The importance of the role that the carbohydrates play in the functions of glycoproteins has been fairly well recognized (Ashwell and Harford, 1982; Kalyan et al., 1982; Kalyan and Bahl, 1983). In recent years, considerable progress has been made toward our understanding of the structure, function, and biosynthesis of the carbohydrates (Kornfeld and Kornfeld, 1985). This has been due largely to the refinement in oligosaccharide separation and structural techniques. A vast amount of structural information gathered as a result has revealed that microheterogeneity is of general occurrence in glycoproteins. The function of this microheterogeneity is ambiguous at present. Moreover, it is difficult to reconcile the phenomenon of microheterogeneity with the fact that there is an intimate and precise relationship between structure and function in biological macromolecules. Nevertheless, the existence of microheterogeneity has complicated the structural determination of the carbohydrate prosthetic groups. In the seventies, microheterogeneity was merely considered as an artifact and was ignored during the structural determination of heterosaccharides. Consequently, the structures reported then were average structures and should be reexamined (Kobata, 1984). In this report, the problem of micro-heterogeneity the general strategy for heterosaccharide structural characterization are considered with respect to three glycoprotein hormones: human choriogonadotropin (hCG), ovine luteinizing hormone (oLH), and equine choriogonadotropin (eCG).

13C-spin-lattice relaxation behavior of acetonitrile and acetone

Spin-lattice relaxation times of all carbon atoms in acetonitrile and acetone were measured at various temperatures. Spin-rotation coupling constants of acetonitrile were determined, and for the methyl carbon atom the following values were found: c⊥=4.5 kHz, c‖= −39 kHz. Considerable contributions of anisotropic-chemical shift relaxation to the nitrile carbon relaxation was detected at lower temperatures with a chemical shift anisotropy of Δσ≈450 ppm. The relaxation behavior of acetone was also studied in aqueous mixtures. Existence of microheterogeneities in the acetone rich concentration range has been concluded from the carbonyl relaxation in D2O, where a considerable contribution from intermolecular proton-carbon interaction was found.