bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical analysis of low‐lying charge transfer states in [Ru(X) (Me)(CO)2(Me‐DAB)] (XCl, I; DAB1,4‐diaza‐1,3‐butadiene) complexes by TDDFT and CASSCF/CASPT2 methods
Authors: Amor N. Ben , Záliš S. , Daniel C. 
Published: May 2006

AbstractThe near‐ultraviolet (UV)/visible electronic spectroscopy of [Ru(X)(Me)(CO)2(Me‐DAB)] (XCl or I; DAB1,4‐diaza‐1,3‐butadiene), model complexes for a series of α‐diimine halide complexes of ruthenium is investigated by means of time‐dependent density functional theory (TDDFT) and complete active space self‐consistent field/CAS second‐order perturbation theory (CASSCF/CASPT2) methods. The convergence on the calculated transition energies to the low‐lying metal‐to‐ligand‐charge‐transfer (MLCT), X‐to‐ligand‐charge‐transfer (XLCT) with X a halide ligand) or sigma‐bond‐to‐ligand‐charge‐transfer (SBLCT) is analyzed for both methods with respect to various methodological aspects: basis set effects and functional influence on the TDDFT results versus the influence of the size and quality of the CASSCF and of the level of the perturbational treatment (single‐state or multi‐state) on the CASSCF/CASPT2 transition energies. On the basis of these accurate calculations, it is shown that whereas the lowest singlet state can be assigned to a nearly pure XLCT state in [Ru(I)(Me)(CO)2(Me‐DAB)], its character is mainly MLCT in [Ru(Cl)(Me)(CO)2(Me‐DAB)], in agreement with time‐resolved emission/infrared (IR) and resonance Raman experimental data. The experimental bands are well reproduced by the CASSCF/CASPT2 calculations despite the difficulty at converging to stable transition energies when enlarging the CASSCF. The TDDFT transitions energies are affected dramatically by the percentage of Hartree–Fock exchange in the hybrid functional. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
THE COVALENT STRUCTURE OF AN ENTIRE γG IMMUNOGLOBULIN MOLECULE
Authors: Edelman Gerald M. , Cunningham Bruce A. , Gall W. Einar , Gottlieb Paul D. , Rutishauser Urs , Waxdal Myron J. 
Published: May 2006

The complete amino acid sequence of a human γG1 immunoglobulin (Eu) has been determined and the arrangement of all of the disulfide bonds has been established. Comparison of the sequence with that of another myeloma protein (He) suggests that the variable regions of heavy and light chains are homologous and similar in length. The constant portion of the heavy chain contains three homology regions each of which is similar in size and homologous to the constant region of the light chain. Each variable region and each constant homology region contains one intrachain disulfide bond. The half-cystines participating in the interchain bonds are all clustered within a stretch of ten residues at the middle of the heavy chains.
These data support the hypothesis that immunoglobulins evolved by gene duplication after early divergence of V genes, which specified antigen-binding functions, and C genes, which specified other functions of antibody molecules. Each polypeptide chain may therefore be specified by two genes, V and C, which are fused to form a single gene (translocation hypothesis). The internal homologies and symmetry of the molecule suggest that homology regions may have similar three-dimensional structures each consisting of a compact domain which contributes to at least one active site (domain hypothesis). Both hypotheses are in accord with the linear regional differential of function in antibody molecules.
CYTOKININS: DISTRIBUTION IN TRANSFER RNA SPECIES OF
Escherichia coli
Authors: Armstrong D. J. , Burrows W. J. , Skoog F. , Roy K. L. , Söll D. 
Published: May 2006

This distribution of cytokinin activity in tRNA species of
Escherichia coli
has been determined. Cytokinin activity was restricted to tRNA species recognizing codons with the initial letter U. The following have been shown to contain a cytokinin: tRNA
Phe
, tRNA
Leu
UUG, tRNA
Ser
UC
G
A
, tRNA
Tyr
, and tRNA
Try
. tRNA
Cys
was present in fractions with cytokinin activity but was not sufficiently pure to prove it to be active. One tRNA
Ser
UC
C
U
species was inactive.

All major tRNA species recognizing condons with initial letters other than U were devoid of cytokinin activity in the tobacco bioassay.
The significance of these findings is discussed as providing a possible mechanism of quantitative modulation at the translation stage of gene-controlled protein biosynthesis.
NUCLEAR AND MITOCHONDRIAL DNA FROM WILD-TYPE AND PETITE YEAST: CIRCULARITY, LENGTH, AND BUOYANT DENSITY
Authors: Billheimer Foster E. , Avers Charlotte J. 
Published: May 2006

Purified mitochondrial and nuclear DNA from diploid isogenic wild-type and vegetative-petite baker's yeast were analyzed by electron microscopy and by analytical ultracentrifugation in CsCl gradients. The buoyant densities in CsCl of nuclear DNA were identical for the two strains (ρ = 1.700), but there was a difference between mitochondrial DNA from the wild type (ρ = 1.684) and the petite (ρ = 1.680). Electron microscopy revealed both circular and linear filaments for nuclear and for mitochondrial DNA of both strains. Nuclear DNA molecules included 6.5 per cent cyclic filaments principally measuring 2 μ or less in contour length, and linear filaments showing a unimodal, disperse length-distribution centered at about 2 to 3 μ, for both strains. Mitochondrial DNA for wild type varied depending upon the method used to extract and purify the molecules; showing only 7.5 per cent circular molecules from CsCl-subfractionated samples, as compared with 15 per cent circles from chloroform-extracted DNA not subjected to CsCl and up to 50 per cent circles from osmotically-lysed mitochondira, as reported in an earlier study. Modal lengths of circles occurred at about 2, 5, and 10 μ Increasing shear degradation also was evident in comparisons of the length-distribution patterns of linear molecules using the three preparative methods. Petite mitochondrial DNA contained 36-38 per cent circular molecules which measured 0.3-5.3 μ, but principally in the range of 0.3 to 2.0 μ whether from chloroform-extracted populations or from ones subfractionated in CsCl. A previous study of osmotically lysed mitochondria had shown a maximum of 8 per cent circles, which we now attribute to a failure, at that time, to detect circles measuring less than 1 μ, a substantial component encountered in the purified DNA samples in the present study. Linear filaments presented a unimodal length distribution in every case.
Despite the variation in molecule populations derived from the three different preparative methods, there were consistent differences between mitochondrial DNA from wild-type and petite yeast in frequencies and size of circular molecules, as well as in length distribution patterns.
Cochlea of the Dolphin,
Tursiops truncatus:
The Basilar Membrane
Authors: Wever Ernest Glen , Mccormick James G. , Palin Jerry , Ridgway S. H. 
Published: May 2006

In the dolphin
Tursiops truncatus
, the basilar membrane over its course its course from basal to apical ends shows a systematic variation in width and in the manner and rigidity of its suspension.

The suspension is by bony laminae on both the outer and inner edges in the basal region, and by progressively less rigid attachments in the more apical regions, until near the apex the membrane is held only by connective tissue.
The basilar membrane shows an unusual variation in width of 14 times, ranging from an astonishingly small value of 25 μm at the basal end to a value toward the apex of about 350 μm. This structural variation is in harmony with the extension of sensitivity of the dolphin ear into the very high frequencies, and suggests unusual capabilities of pitch discrimination in this high range.
Adenyl Cyclase as a Link between Photon Capture and Changes in Membrane Permeability of Frog Photoreceptors
Authors: Bitensky Mark W. , Gorman Ronnie E. , Miller William H. 
Published: May 2006

Tomita has shown by electrophysiological measurements that the photoreceptors of the vertebrate retina are depolarized (excited) by darkness and hyperpolarized (inhibited) by light. Excitation is accompanied by an increase, and inhibition by a decrease, in the sodiumion permeability of the receptor cell.
The retinal-rod outer segments of the frog contain an adenyl cyclase that is active in darkness and inactivated by light. This cyclase has a specific activity ten-times higher than the activity in previously described tissues. It is suggested that cyclic AMP is an intermediate in the light- and dark-induced changes in sodium permeability in the photoreceptor cell.
Stimulation of the Proliferation of Chicken Fibroblasts by Folic Acid or a Serum Factor(s) in a Plasma-Containing Medium
Authors: Balk Samuel D. 
Published: May 2006

The proliferation of chicken fibroblasts is strongly stimulated by folic acid, at greater than physiological concentrations, in a plasma-containing medium, or by serum in a medium of physiological folic acid concentration. Serum and plasma, however, do not appear to differ in their content of folic acid derivatives.
A qualitative difference between the proliferative behaviors of normal and transformed fibroblasts is obtained when these cells are cultivated in a physiological-folate-low-calcium-plasma medium. In such a medium, transformants proliferate steadily, at a significant rate, while normal fibroblasts do not multiply at all.
Defective Formation of the Lamellar Cytoplasm by Neoplastic Fibroblasts
Authors: Domnina L. V. , Ivanova O. Y. , Margolis L. B. , Olshevskaja L. V. , Rovensky Y. A. , Vasiliev J. M. , Gelfand I. M. 
Published: May 2006

Isolated cultures of mouse L-cells are similar to those of normal cells in showing contact inhibition of movement and topoinhibition of growth. In mixed cultures with untransformed mouse embryo fibroblasts, their parent strain, however, L cells are able to form colonies above the monolayer of normal fibroblasts, i.e., they have a property characteristic of transformed cells. Analysis of microcinematographic data suggests that the behavior of L cells in mixed cultures is a result of their defective attachment to the substratum. Scanning electron microscopy showed that attachment of a normal fibroblast was accompanied by the formation of a wide ring of flattened cytoplasm spread on the substratum (lamellar cytoplasm). This structure was observed to disintegrate in newly attached L cells. The structure of the lamellar cytoplasm remained abnormal in the fully spread L cells. The mean area of lamellar cytoplasm was 3- to 4-times less in L cells than in normal fibroblasts.
It is suggested that deficient formation of lamellar cytoplasm may be the basis of the inability of L cells to interact normally with embryo fibroblasts.
Self-Association of Gene-32 Protein of Bacteriophage T4
Authors: Carroll Robert B. , Neet Kenneth E. , Goldthwait David A. 
Published: May 2006

The self-association of gene-32 protein has been studied by sedimentation equilibrium centrifugation and polyacrylamide gel electrophoresis, in order to better understand its role in DNA replication and genetic recombination. The monomer molecular weight of gene-32 protein is 38,000 in guanidine hydrochloride and 34,000 in sodium dodecyl sulfate, in agreement with the results of Alberts and coworkers. Stable dimers of gene-32 protein occur under various conditions, among which are high ionic strength and pH 10. The occurrence of stable dimers under some conditions and higher aggregates under others indicates there are two types of protein-protein interactions occurring in gene-32 protein self-association. The association that occurs above about 0.1 mg/ml concentration of protein produces at least decamers.
A model for the DNA replication fork is postulated that requires the two different interactions that occur in gene-32 protein aggregation. In the model, gene-32 protein holds the two strands of the DNA duplex in a conformation that prevents their reannealing and, therefore, facilitates replication and recombination.
Self-Complementarity of Terminal Sequences Within Plus or Minus Strands of Adenovirus-Associated Virus DNA
Authors: Koczot Frank J. , Carter Barrie J. , Garon Claude F. , Rose James A. 
Published: May 2006

At least 70% of plus or minus strands of adenovirus-associated virus DNA contain self-complementary sequences at or near their termini. Self-annealing of these sequences generates circular molecules that are closed by duplex, hydrogen-bonded segments. The self-annealed segments are sensitive to exonuclease III and have a thermal stability comparable to that of double-stranded DNA molecules. Length measurements of double-stranded adenovirus-associated virus DNA molecules show a bimodal distribution, with the larger component being 10% shorter than SV40 DNA.
The presence of self-complementary terminal sequences in single-stranded molecules of viral DNA has been observed previously only with DNA from adenoviruses. It is thus especially notable that adenovirus-associated virus replication is unconditionally dependent on a helper adenovirus. A possible role for terminal self-complementary sequences in viral DNA replication is suggested.
Structural Characteristics of Some Murine RNA Tumor Viruses Studied by Lactoperoxidase Iodination
Authors: Witte Owen N. , Weissman Irving L. , Kaplan Henry S. 
Published: May 2006

Iodination by the noninvasive enzymatic lactoperoxidase technique has been used to study the enzyme-accessible and enzyme-inaccessible proteins of three oncorna viruses (radiation leukemia virus, Moloney leukemia virus, and mouse mammary tumor virus).
The number and relative molecular weight of proteins associated with virion preparations purified on sucrose gradients were characterized by scans of Coomassie blue-stained bands after dodecyl sulfate-polyacrylamide gel electrophoresis. Gel scans from the leukemia viruses are similar, each showing six distinct major protein bands on stained gels. The mammary tumor virus proteins by this analysis are not similar to those of the leukemia viruses.
Enzymatic iodination of intact virion preparations led to the solitary labeling of one of the major proteins of each virus—the 80,000-dalton protein of the leukemia viruses and the 52,500-dalton protein of the mammary tumor virus. These are tentatively positioned as surface (enzyme-accessible) moieties in the virions. Disruption of each virus with a nonionic nonionic detergent before enzymatic iodination led to the labeling of the remaining stainable bands. The four lower molecular weight bands of the leukemia viruses are tentatively positioned as internal (enzyme-inaccessible) components.
Mitochondrial Protein Synthesis: RNA with the Properties of Eukaryotic Messenger RNA
Authors: Perlman S. , Abelson H. T. , Penman S. 
Published: May 2006

A heterogeneous RNA fraction with properties resembling those of messenger RNA was identified in mammalian mitochondria. Synthesis of contaminating RNA of nuclear origin was suppressed by treatment with camptothecin. Labeling of the messenger-like RNA is completely inhibited by ethidium bromide, a specific inhibitor of mitochondrial functions.
Although mitochondrial protein synthesis resembles that of prokaryotes in several regards, the messenger-like RNA is covalently linked to poly(adenylic acid) [poly(A)]. Poly(A) has thus far been found only in eukaryotic cells. The poly(A) segment has a gel electrophoretic mobility of about 4 S, corresponding to a length of 50-80 nucleotides, and thus resembles in size the poly(A) found in some mammalian viral RNAs. The messenger RNA can be released from the mitochondrial protein-synthesizing structure by treatment with puromycin.
Lung Collagen Heterogeneity
Authors: Bradley Kathryn , McConnell-Breul Sally , Crystal Ronald G. 
Published: May 2006

The structural heterogeneity of rabbit lung collagen was examined by extracting labeled collagen from short-term cultures of lung minces with 1 M NaCl-50 mM Tris·HCl (pH 7.4), 0.5 M acetic acid, or 0.4 ionic strength phosphate buffer. The extracted collagens were purified by carboxymethyl-cellulose chromatography, and their cyanogen bromide peptides were mapped by ion exchange chromatography and acrylamide gels. Rabbit skin α1(I) and α2 chains and rabbit sternal cartilage α1(II) chains were used as markers.
The peripheral lung, containing alveoli, small blood vessels, and small airways, synthesized α1(I) and α2 chains. The trachea and the bronchial tree (first through seventh order branches) both synthesized α1(II) chains. Lung α1(I), α2, and α1(II) chains all have a molecular weight of about 100,000 and are all sensitive to Clostridial collagenase.

The extraction and purification methods used isolate only 50% of the collagen synthesized by these structures
in vitro
. Once all collagen types in lung can be described and quantitated, it should be possible to utilize lung collagen types as biochemical markers to study normal lung development and to define the lung fibrotic diseases.
Self-association of hemoglobin β
SH
chains is linked to oxygenation
Authors: Valdes Roland , Ackers Gary K. 
Published: May 2006

Self-association of unliganded β
SH
chains into tetramers (4 β
1
[unk] β
4
) is experimentally found to be energetically less favorable (Δ
G
0
= -19.05 ± 0.30 kcal) than the corresponding oligomerization of fully oxygenated chains (4 β
1
X [unk] β
4
X
4
; Δ
G
0
= -22.45 ± 0.35 kcal). Hence the tetramers must bind oxygen with a higher affinity than that of dissociated chains. Calculations are presented showing why this affinity difference is not easily detected. The linkage is in a direction opposite to that exhibited by normal hemoglobin A, in which oligomerization of high-affinity unliganded dimers (2 αβ [unk] α
2
β
2
) leads to tetramers with decreased oxygen affinity. In contrast, the oligomerization of high-affinity, unliganded β
SH
chains leads to tetramers with even higher affinity. The results imply the existence of at least two conformational states for β chains.

Effects of inositol hexaphosphate on β chain association were investigated. Inositol hexaphosphate was found to have no measurable effect at pH 7.4, in contrast to pH 7 where very pronounced effects have been observed. Some theoretical aspects of the linkages are presented and the relationship of the findings to concepts of structural transition and allosteric regulation is discussed.
In contrast to the β chains, self-association of α chains into dimers was found to occur with the same free energy in both unliganded and fully oxygenated states. Thus, the self-association of α chains is not linked to oxygenation.
Membrane Stretch Slows the Concerted Step prior to Opening in a Kv Channel
Authors: Laitko Ulrike , Juranka Peter F. , Morris Catherine E. 
Published: May 2006

In the simplest model of channel mechanosensitivity, expanded states are favored by stretch. We showed previously that stretch accelerates voltage-dependent activation and slow inactivation in a Kv channel, but whether these transitions involve expansions is unknown. Thus, while voltage-gated channels are mechanosensitive, it is not clear whether the simplest model applies. For Kv pore opening steps, however, there is excellent evidence for concerted expansion motions. To ask how these motions respond to stretch, therefore, we have used a Kv1 mutant, Shaker ILT, in which the step immediately prior to opening is rate limiting for voltage-dependent current.
Macroscopic currents were measured in oocyte patches before, during, and after stretch. Invariably, and directly counter to prediction for expansion-derived free energy, ILT current activation (which is limited by the concerted step prior to pore opening) slowed with stretch and the g(V) curve reversibly right shifted. In WTIR (wild type, inactivation removed), the g(V) (which reflects independent voltage sensor motions) is left shifted. Stretch-induced slowing of ILT activation was fully accounted for by a decreased basic forward rate, with no change of gating charge. We suggest that for the highly cooperative motions of ILT activation, stretch-induced disordering of the lipid channel interface may yield an entropy increase that dominates over any stretch facilitation of expanded states. Since tail current τ(V) reports on the opposite (closing) motions, ILT and WTIR τ(V)tail were determined, but the stretch responses were too complex to shed much light.
Shaw is the Kv3 whose voltage sensor, introduced into Shaker, forms the chimera that ILT mimics. Since Shaw2 F335A activation was reportedly a first-order concerted transition, we thought its activation might, like ILT's, slow with stretch. However, Shaw2 F335A activation proved to be sigmoid shaped, so its rate-limiting transition was not a concerted pore-opening transition. Moreover, stretch, via an unidentified non–rate-limiting transition, augmented steady-state current in Shaw2 F335A.
Since putative area expansion and compaction during ILT pore opening and closing were not the energetically consequential determinants of stretch modulation, models incorporating fine details of bilayer structural forces will probably be needed to explain how, for Kv channels, bilayer stretch slows some transitions while accelerating others.
The relationship between gross motor function and participation restriction in children with cerebral palsy: an exploratory analysis
Authors: Kerr C. , McDowell B. , McDonough S. 
Published: May 2006

AbstractBackground  Children with cerebral palsy (CP) experience a variety of functional limitations depending on the severity of their condition that impact on their participation in day‐to‐day activities.Methods  The gross motor function and participation restrictions experienced by 60 ambulant children with CP (mean age 11.04 years) were assessed using the Gross Motor Function Measure (GMFM‐88) and the Lifestyle Assessment Questionnaire – Cerebral Palsy (LAQ‐CP).Results  A significant negative correlation existed between the GMFM‐88 and the LAQ‐CP (r = −0.52, P < 0.001). Significant relationships were also identified between the GMFM‐88 and the physical independence, mobility, economic burden and social integration domains of the LAQ‐CP.Conclusion  In ambulatory children with CP, better physical function is associated with a lesser impact of disability; however, the relationship between function and participation is complex. Measures of participation restriction may assist with goal setting appropriate to the specific needs of the child and family.
A matched case–control study: investigating the relationship between youth assets and sexual intercourse among 13‐ to 14‐year‐olds
Authors: Doss J. R. , Vesely S. K. , Oman R. F. , Aspy C. B. , Tolma E. , Rodine S. , Marshall L. 
Published: May 2006

AbstractBackground  The number of teenagers engaging in sexual intercourse has consistently changed over the past several years. This can become a major challenge when trying to determine why teens continue to have sex. The purpose of this paper was to investigate the relationship between youth assets and sexual intercourse among 13‐ to 14‐year‐olds.Methods  Cross‐sectional data were collected using in‐person at‐home interviews from a random sample of inner‐city neighbourhood 13‐ to 14‐year‐old teenagers (n = 64 matched pairs; 36% 13‐year‐olds, 53% female, 45% white, 28% African‐American, 16% Hispanic and 11% Native American). Nine individual youth assets were analysed using conditional logistic regression (matching for several demographic variables) to assess the association between assets and abstinence in younger teens.Results  Conditional logistic regression analyses showed that two assets, positive Peer Role Models [odds ratios (OR) = 4.67, 95% confidence intervals (CI) = 1.93, 11.27] and Use of Time (Religion) (OR = 2.20, 95% CI = 1.04, 4.65), were significantly related (P < 0.05) to younger teens never having engaged in sexual activity.Conclusion  These findings suggest, when considering abstinence behaviour, involvement in religious activities and having positive peer role models appear to be protective factors related to delaying sexual intercourse among teens aged 13–14 years.