Comparative cytogenetics of bats (Chiroptera): The prevalence of Robertsonian translocations limits the power of chromosomal characters in resolving interfamily phylogenetic relationships

Although the monophyly of Chiroptera is well supported by many independent studies, higher-level systematics, e.g. the monophyly of microbats, remains disputed by morphological and molecular studies. Chromosomal rearrangements, as one type of rare genomic changes, have become increasingly popular in phylogenetic studies as alternatives to molecular and other morphological characters. Here, the representatives of families Megadermatidae and Emballonuridae are studied by comparative chromosome painting for the first time. The results have been integrated into published comparative maps, providing an opportunity to assess genome-wide chromosomal homologies between the representatives of eight bat families. Our results further substantiate the wide occurrence of Robertsonian translocations in bats, with the possible involvement of whole-arm reciprocal translocations (WARTs). In order to search for valid cytogenetic signature(s) for each family and superfamily, evolutionary chromosomal rearrangements identified by chromosomal painting and/or banding comparison are subjected to two independent analyses: (1) a cladistic analysis using parsimony and (2) the mapping of these chromosomal changes onto the molecularly defined phylogenetic tree available fromthe literature. Both analyses clearly indicate the prevalence of homoplasic events that reduce the reliability of chromosomal characters for resolving interfamily relationships in bats.

Substitution Matrices of Residue Triplets Derived from Protein Blocks.

In protein sequence alignment, residue similarity is usually evaluated by substitution matrix, which scores all possible exchanges of one amino acid with another. Several matrices are widely used in sequence alignment, including PAM matrices derived from homologous sequence and BLOSUM matrices derived from aligned segments of BLOCKS. However, most matrices have not addressed the high-order residue-residue interactions that are vital to the bioproperties of protein.With consideration for the inherent correlation in residue triplet, we present a new scoring scheme for sequence alignment. Protein sequence is treated as overlapping and successive 3-residue segments. Two edge residues of a triplet are clustered into hydrophobic or polar categories, respectively. Protein sequence is then rewritten into triplet sequence with 2 · 20 · 2 = 80 alphabets. Using a traditional approach, we construct a new scoring scheme named TLESUMhp (TripLEt SUbstitution Matrices with hydropobic and polar information) for pairwise substitution of triplets, which characterizes the similarity of residue triplets. The applications of this matrix led to marked improvements in multiple sequence alignment and in searching structurally alike residue segments. The reason for the occurrence of the ‘‘twilight zone,’’ i.e., structure explosion of lowidentity sequences, is also discussed.

Chromosomal aberrations induced by C-12(6+) ions and Co-60 gamma-rays in mouse immature oocytes

The ovaries of Kun-Ming strain mice (3 weeks) were irradiated with different doses of C-12(6+) ion or Co-60 gamma-ray. Chromosomal aberrations were analyzed in metaphase II oocytes at 7 weeks after irradiation. The relative biological effectiveness (RBE) of C C-12(6+) ion was calculated with respect to Co-60 gamma-ray for the induction of chromosornal aberrations. The C-12(6+) ion and Co-60 gamma-ray dose-response relationships for chromosomal aberrations were plotted by linear quadratic models. The data showed that there was a dose-related increase in frequency of chromosomal aberrations in all the treated groups compared to controls. The RBE values for C-12(6+) ions relative to (CO)-C-60 gamma-rays were 2.49, 2.29, 1.57, 1.42 or 1.32 for the doses of 0.5, 1.0, 2.07 4.0 or 6.0 Gy, respectively. Moreover, a different distribution of the various types of aberrations has been found for C-12(6+) ion and Co-60 gamma-ray irradiations. The dose-response relationships for C-12(6+) ion and (CO)-C-60 gamma-ray exhibited positive correlations. The results from the present study may be helpful for assessing genetic damage following exposure of immature oocytes to ionizing radiation.

The level and distribution of chromosomal aberration of tomato seeds at different penetration depths of carbon ions

The relationship between the penetration depth and the level and distribution of chromosomal aberration of the root tip cells were investigated by exposure of the superposed tomato seeds to 80 MeV/u carbon ions. The results showed that on the entrance of the beam the chromosomal aberration level was low. Damage such as breaks and gaps were dominant. At the Bragg peak, the chromosomal aberration level was high. The yields of dicentrics, rings and disintegrated small chromosomes increased but the yields of breaks and gaps decreased. These results are consistent with the distribution of the physical depth dose pro. le of carbon ions. It is effective to deposit the Bragg peak on the seeds to induce hereditary aberration in the mutation breeding with heavy ions.

Effect of substitution of chromium for nickel on structure and electrochemical characteristic of Ti0.26Zr0.07V0.24Mn0.1Ni0.33 multi-phase hydrogen storage alloy

Ti-Zr-V-Mn-Ni-based multi-component alloys demonstrate high discharge capacity in KOH electrolyte. However, the drastic decrease in their discharge capacities makes them unsuitable for use as negative electrode material in the Ni/MH battery. In present work, Ni is partially replaced by Cr in the Ti-Zr-V-Mn-Ni-based alloys to improve their cycle life. The effects of Cr substitution on microstructures and the electrochemical characteristics of the alloys are investigated. It is found that Cr substitution is very effective to improve the cyclic durability of the alloys although the discharge capacity decreases with changing x from 0.05 to 0.20. Some kinetic performances have been also investigated using electrochemical impedance spectroscopy (EIS) and potentiostatic discharge technique.

Preparation and characterization of cationic corn starch with a high degree of substitution in dioxane-THF-water media

Cationic corn starch derivatives with a high degree of substitution are prepared in alkaline solution or in mixed media of organic solvent and water with different levels of the cationic reagent, 2,3-epoxypropyltrimethylammonium chloride. The starch cationization yield is investigated, and the results indicate that the degree of substitution (DS) of the samples depends on the reaction conditions and reaction media. The maximum DS values are up to 1.37 in 1,4-dioxane alkali ne-aqueous solution. Meanwhile, the structures of the cationic starch derivatives are characterized by elemental analyses, FTIR spectroscopy, X-ray diffraction, and C-13 NMR spectroscopy, as well as by SEM techniques.

Effect of strontium substitution on the activity of La2-xSrxNiO4 (x=0.0-1.2) in NO decomposition

The aim of this work is to study the effect of Sr substitution on the redox properties and catalytic activity of La2-xSrxNiO4 (x = 0.0-1.2) for NO decomposition. Results suggest that the x = 0.6 sample shows the highest activity. The characterization (TPD, TPR, etc.) of samples indicates that the x = 0.6 sample possesses suitable abilities in both oxidation and reduction, which facilitates the proceeding of oxygen desorption and NO adsorption. At temperature below 700 degrees C, the oxygen desorption is difficult, and is the rate-determining step of NO decomposition. With the increase of reaction temperature (T > 700 degrees C), the oxygen desorption is favorable and, the active adsorption of NO on the active site (NO + V-o + Ni2+ -> NO--Ni3+) turns out to be the rate-determining step. The existence of oxygen vacancy is the prerequisite condition for NO decomposition, but its quantity does not relate much to the activity.

Substitution effect of nitrogen atoms with carbon atoms in porphyrin on the electronic structure and excited states properties

Density functional theory (DFT) electronic structure calculations were carried out to predict the structures and the absorption and emission spectra for porphyrin and a series of carbaporphyrins-carbaporphyrin, adj-dicarbaporphyrin, opp-dicarbaporphyrin, tricarbaporphyrin and tetracarbaporphyrin. The ground- and excited-state geometries were optimized at the B3LYP/6-31g(d) and CIS/6-31g(d) level, respectively. The optimized ground-state geometry and absorption spectra of porphyrin, calculated by DFT and time-dependent DFT (TDDFT), are comparable with the available experimental values. Based on the optimized excited-state geometries obtained by CIS/6-31g(d) method, the emission properties are calculated using TDDFT method at the B3LYP/6-31g(d) level. The effects of the substitution of nitrogen atoms with carbon atoms at the center positions of porphyrin are discussed. The results indicate that the two-pyrrole nitrogens are important to the chemical and physical properties for porphyrin.

Preparation of divalent rare earth ions in air by aliovalent substitution and spectroscopic properties of Ln(2+)

When alkaline earth ions in borates, phosphates or borophosphates [SrB4O7, SrB6O10, BaB8O13, MBPO5 (M=Ca,Sr)] are substituted partially and aliovalently by trivalent rare earth ions such as Sm3+, Eu3+, these rare earth ions can be reduced to divalent state by the produced negative charge vacancy V-M". The matrices must have appropriate structure containing a rigid three-dimensional network of tetragonal AO(4) groups (A=B,P). These groups can surround and isolate the produced divalent RE2+ ions from the reaction with oxygen. Therefore, this reduction reaction can be carried out even in air at high temperature. The produced divalent rare earth ions can be detected by luminescence and XANES methods and their spectroscopic properties are discussed.

Advances in gas-phase electrophilic aromatic substitution reaction

Recent advances in the gas - phase reaction of aromatics with cationic electrophiles are reviewed. The overall substitution reaction is analyzed in terms of its elementary steps. Mechanistic studies have been focused on the structure and reactivity of covalent and non - covalent ionic intermediates, which display a rich chemistry and provide benchmark reactivity models. Particular attention has been devoted to proton transfer reactions, which may occur intra or intermolecularly in arenium intermediates.

Effect of end substitution on optical properties and molecular orientation of distyrylbenzene derivatives in thin film

Three distyrylbenzene (DSB) derivatives were vacuum-evaporated on a (001) surface of KBr. DSB derivative molecules formed nuclei by interaction between the electron donative methoxyl group and Br- ion of the substrate crystal and oriented their longitudinal axis obliquely to the substrate surface. The peak shift between the emission peaks of solution and film decreased depending on the number of substituent. This phenomenon was originated to reduction of molecular interaction between neighboring molecules by steric hindrance of end substituents. (C) 2000 Elsevier Science S.A. All rights reserved.

The application and a substitution defect model for Eu3+ -> Eu2+ reduction in non-reducing atmospheres in borates containing BO4 anion groups

The variations of emission intensities of SrB4O7:Eu2+ and Sr2B5O9Cl:Eu2+ prepared in different atmospheres are discussed in view of the structure of host compounds. A model of substitution defects is proposed to explain the abnormal reduction of Eu3+ --> Eu2+ in non-reducing atmospheres of N-2, air and O-2. Experiment results show that SrB4O7:Eu2+ phosphor sample prepared in N-2 atmosphere has an emission intensity of 94% as high as that of the sample prepared in H-2 gas. This implies that the reduction of Eu2+ --> Eu2+ in non-reducing atmospheres could be potentially used in preparing phosphors, such as SrB4O7:Eu2+. (C) 1999 Elsevier Science Ltd. All rights reserved.

Vibronic transitions and site substitution of Eu2+ and codoped ions in KMgF3 : Eu-X (X=Ce, Cr, Gd, Cu) system

The high-resolution emission spectra of KMgF3 : Eu and KMgF3 : Eu-X(X = Ce, Cr, Gd, Cu) single crystals were measured at 300 and 77 K. The vibronic side bands of Eu2+ were characterized and an assignment of the normal mode frequencies to particular vibrations has been made. The correlation between the vibronic frequencies of Eu2+ and the site substitution of other co-dopcd ions was first found. The relationship between vibronic intensity of Eu2+ and other doped ions concentration showed that Cr3+, Gd3+ ions competed K+ sites with Eu2+ ions. Ce3+ and Eu3+ occurred the electron transference. The introduction of Cu+ made for Eu2+ substuting for K+ sites.

Site substitution and energy transfer of Eu2+ and Ce3+ in KMgF3 : Eu and KMgF3 : Eu-Ce single crystals

The high-resolution emission spectra of KMgF3 : Eu and KMgF3 : Eu-Ce single crystals were measured at 77 K. The site substitution of Eu2+ and Eu2+-Ce3+ co-doped system in KMgF3 was discussed. Eu2+ substituted for K+ sites on three different site-symmetry: cubic, trigonal and tetragonal. The attribution of all lines occurring in the emission spectra were ascertained. The indirect energy transfer from P-6(5/2) states of Eu2+ to 4f5d states of Ce3+ in KMgF3 : Eu-Ce was observed and the energy transfer mechanism was studied. The d-d interaction among levels was proposed.