bluuebunny/crossref_metadata_2025 huggingface dataset:
Identification of a calcium-binding protein as a calcium-dependent regulator of brain adenylate cyclase.
Authors: Brostrom C O , Huang Y C , Breckenridge B M , Wolff D J
Published: May 2006

An activating factor of adenylate cyclase (EC 4.6.1.1) HAS BEEN OBTAINED FROM DETERGENT-DISPERSED PREPARATIONS OF PORCINE CEREBRAL CORTEX BY COLUMN CHROMATOGRAPHY ON ECTEOLA-cellulose. The factor was identified by acrylamide gel electrophoresis and by enzyme activation studies as the Ca2+-binding protein that regulates the activity of a brain cyclic nucleotide phosphodiesterase. This Ca2+-binding protein confers a Ca2+-dependent activation upon the adenylate cyclase, which is reversed by the subsequent addition of egta in excess of the free Ca2+. It is proposed that this Ca2+-dependent regulator controls enzymatic activities responsible for the synthesis of adenosine 3':5'-monophosphate and for the hydrolysis of guanosine 3':5'-monophosphate.
Stochastic models for the Earth's relief, the shape and the fractal dimension of the coastlines, and the number-area rule for islands
Authors: Mandelbrot Benoit B.
Published: May 2006

The degree of irregularity in oceanic coastlines and in vertical sections of the Earth, the distribution of the numbers of islands according to area, and the commonality of global shape between continents and islands, all suggest that the Earth's surface is statistically self-similar. The preferred parameter, one which increases with the degree of irregularity, is the fractal dimension,
D
, of the coastline; it is a fraction between 1 (limit of a smooth curve) and 2 (limit of a plane-filling curve). A rough Poisson-Brown stochastic model gives a good first approximation account of the relief, by assuming it to be created by superposing very many, very small cliffs, placed along straight faults and statistically independent. However, the relative area predicted for the largest islands is too small, and the irregularity predicted for the relief is excessive for most applications; so is indeed the value of the dimension, which is
D
= 1.5. Several higher approximation self-similar models are described. Any can be matched to the empirically observed
D
, and can link all the observations together, but the required self-similarity cannot yet be fully explained.
Control of oscillating glycolysis of yeast by stochastic, periodic, and steady source of substrate: a model and experimental study.
Authors: Boiteux A , Goldbeter A , Hess B
Published: May 2006

Type and range of entrainment of glycolytic oscillations by a periodic source of substrate are determined experimentally in yeast extracts. Subharmonic entrainment proves the nonlinear nature of the glycolytic oscillator Random variation of the substrate input yields sustained oscillations of irregular waveform and stable period. The results agree with the predictions of an allosteric model for phosphofructokinase (EC 2.7.1.11; ATP:D-fructose-6-phosphate 1-phosphotransferase), which is the enzyme responsible for periodic operation of glycolysis. A comparison between model and experiment in the case of a constant source of substrate further indicates that the oscillatory dynamics of the glycolytic system can satisfactorily be described by the phosphofructokinase model.
Translation of thyroglobulin 33S messenger RNA as a means of determining thyroglobulin quaternary structure.
Authors: Vassart G , Refetoff S , Brocas H , Dinsart C , Dumont J E
Published: May 2006

Thyroglobulin is a 19S protein of approximately 660,000 daltons and unknown quaternary structure. We have previously shown that a 33S mRNA purified from mammalian thyroids promoted synthesis in the Xenopus oocyte of a peptide immunologically related to thyroglobulin. Chemical identity to the native protein is now presented by means of a tryptic peptide analysis. Moreover, the 33S mRNA is shown to contain all the information required for the synthesis of a complete 19S thyroglobulin molecule. Gel filtration in Sepharose under denaturing conditions indicates that the reduced polypeptide encoded by the 33S mRNA is larger than 210,000 daltons. A model of a dimeric thyroglobulin with about 300,000 dalton subunits is presented.
Imbalanced globin chain synthesis in heterozygous beta-thalassemic bone marrow.
Authors: Chalevelakis G , Clegg J B , Weatherall D J
Published: May 2006

Globin synthesis was studied in the bone marrow of seven heterozygous beta-thalassemic subjects. We found evidence of significant imbalance of alpha- and beta-chain production particularly at short times of incubation. There was a progressive decrease in alpha/beta-chain production ratio with increasing incubation time which was due to a decreased rate of net alpha-chain production, indicating that a large proportion of the newly synthesized alpha chains are degraded, particularly in bone marrow, within a few minutes of synthesis, leading to relatively low alpha/beta ratios if these are measured solely at incubation times greater than 10 min. The significant degradation of excess alpha chains explains why inclusion body formation and ineffective erythropoiesis, notable in beta-thalassemia homozygotes where there is gross chain imbalance, are not observed to any marked degree in heterozygotes.
Cell-free synthesis of human interferon.
Authors: Pestka S , McInnes J , Havell E A , Vilcek J
Published: May 2006

With mRNA prepared from induced human fibroblasts biologically active human interferon was synthesized de novo in a cell-free extract from mouse cells. The identity of the antiviral activity as human interferon was demonstrated by its species and antigenic specificity.
Analysis of DNA of isolated chromatin subunits.
Authors: Lacy E , Axel R
Published: May 2006

Partial digestion of rat liver nuclei with staphylococcal nuclease results in the liberation of nucleo-protein complexes consisting of one or more upsilon bodies. By velocity centrifugation we have isolated the monomeric subunit in relatively pure form. We find that this subunit contains 185 base pairs of DNA and 240,000 daltons of protein, resulting in a protein to DNA ratio identical to that of unperturbed chromatin. The isolated monomeric particle is further susceptible to internal nuclease attack resulting in the solubilization of 46% of the monomeric DNA. Analysis of the resistant DNA reveals a complex but highly reproducible pattern of DNA fragments ranging from 160 to 60 base pairs in length. Analysis of the reassociation kinetics of the isolated subunit DNA reveals that most, if not all genomic sequences, are involved in this basic subunit structure. No special frequency class of DNA is absent from upsilon bodies. Furthermore, virtually all liver sequences transcribed into mRNA are present in upsilon body DNA. These results indicate that upsilon body formation may be random with respect to DNA sequence and suggest that the mere presence of upsilon bodies over a specific region of DNA is not sufficient to restrict its transcription.
Normal and mutant thermotaxis in the nematode Caenorhabditis elegans.
Authors: Hedgecock E M , Russell R L
Published: May 2006

When grown at a temperature from 16 degrees to 25 degrees and placed on a thermal gradient, the nematode Caenorhabditis elegans migrates to its growth temperature and then moves isothermally. Behavioral adaptation to a new temperature takes several hours. Starved animals, in contrast, disperse from the growth temperature. Several mutants selected for chemotaxis defects have thermotaxis defects as well; these behaviors depend on some common gene products. New mutants selected directly for thermotaxis defects have unusual phenotypes which suggest mechanisms for thermotaxis.
Induction by alkylating agents of sister chromatid exchanges and chromatid breaks in Fanconi's anemia.
Authors: Latt S A , Stetten G , Juergens L A , Buchanan G R , Gerald P S
Published: May 2006

Sister chromatid exchanges, which may reflect chromosome repair in response to certain types of DNA damage, provide a means of investigating the increased chromosome fragility characteristic of Fanconi's anemia. By a recently developed technique using 33258 Hoechst and 5-bromodeoxyuridine, it was observed that the baseline frequency of sister chromatid exchanges in phytohemagglutinin-stimulated lymphocytes from four males with Fanconi's anemia differed little from that of normal lymphocytes. However, addition of the bifunctional alkylating agent mitomycin C (0.01 or 0.03 mug/ml) to the Fanconi's anemia cells during culture induces less than half of the increase in exchanges found in identically treated normal lymphocytes. This reduced increment in exchanges in accompanied by a partial suppression of mitosis and a marked increase in chromatid breaks and rearrangements. Many of these events occur at sites of incomplete chromatid interchange. The increase in sister chromatid exchanges induced in Fanconi's anemia lymphocytes by the monofunctional alkylating agent ethylmethane sulfonate (0.25 mg/ml) was slightly less than that in normal cells. Lymphocytes from two sets of parents of the patients with Fanconi's anemia exhibited a normal response to alkylating agents, while dermal fibroblasts from two different patients with Fanconi's anemia reacted to mitomycin C with an increase in chromatid breaks, but a nearly normal increment of sister chromatid exchanges. The results suggest that chromosomal breaks and rearrangements in Fanconi's anemia lymphocytes may result from a defect in a form of repair of DNA damage.
Absence of interference in photoexcitation of triplets
Authors: Felix C. C. , Weissman S. I.
Published: May 2006

Kinetics of growth and decay of triplet states of molecules at known orientation in a magnetic field have been measured. Amplitudes of the zero field eigenstates in each of the eigenstates at finite field were varied by choice of orientation. No interference between the amplitudes of the zero field states was found in the observed kinetics. It is concluded that excitations into the individual zero field components proceed via independent channels.
Translation of RNA that contains polyadenylate from yeast mitochondria in an Escherichia coli ribosomal system.
Authors: Padmanaban G , Hendler F , Patzer J , Ryan R , Rabinowitz M
Published: May 2006

RNA that contains poly(A) [poly(A)-RNA] has been isolated from yeast mitochondria by poly(U) Sepharose-4B column chromatography. Pulse-labeled poly(A)-RNA shows 8-10 discrete peaks by acrylamide gel electrophoresis. The specific activity of mitochondrial poly(A)-RAN is six to eight times greater than that of mitochondrial rRNA after pulse labeling of protoplasts with [3H-]uridine. Ethidium bromide inhibits incorporation by over 90%. The total mitochondrial RNA preparation was contaminated with 5-15% cytoplasmic rRNA as determined by gel electrophoresis, but RNA exhaustion hybridization experiments indicated little or no cytoplasmic contamination of the mitochondrial poly(A)-RNA. The poly(A)-RNA stimulates [3H]leucine incorporation into protein in an E. coli cell-free system. A fraction of the labeled product is precipitated with antibody directed toward yeast cytochrome oxidase, but not with antibody directed toward bovine serum albumin. Sodium dodecyl sulfate gel electrophoresis of the immunoprecipitated material reveals labeled peptides having the mobility of the three larger cytochrome oxidase peptides, which are known to be translated by mitochondrial ribosomes.
Structure of transcriptionally active chromatin.
Authors: Gottesfeld J M , Murphy R F , Bonner J
Published: May 2006

Rat-liver chromatin has bee fractionated into transcriptionally active and inactive regions [Gottesfeld et al. (1974) Proc. Nat. Acad. Sci. USA 71, 2193-2197] and the distribution of nuclease-resistant complexes in these fractions has been investigated. About half of the DNA of both fractions is resistant to attack by tne endonuclease DNase II. The nuclease-resistant structures of inactive chromatin are DNA-histone complexes (v-bodies) which sediment at 11-13 S. Template-active chromatin yields two peaks of nuclease-resistant nucleoprotein. These complexes sediment at 14 and 19 S, and contain DNA, RNA, histone, and nonhistone chromosomal proteins. Polyacrylamide gel electrophoresis reveals a complex pattern of chromatin proteins, suggesting that the complexes are heterogeneous in composition.
Local anesthetics affect transmembrane cytoskeletal control of mobility and distribution of cell surface receptors.
Authors: Poste G , Papahadjopoulos D , Nicolson G L
Published: May 2006

Tertiary amine local anesthetics facilitated concanavalin A-induced redistribution of lectin receptors on murine BALB/3T3 cells and enhanced the susceptibility of these cells to agglutination by concanavalin A. In contrast, these drugs at similar concentrations inhibited ligand-induced capping of immunoglobulin receptors on mouse lymphocytes. We propose that these differing effects of local anesthetics on membrane receptor mobility in fibroblasts and lymphocytes result from the action of anesthetics on membrane-associated microtubules and microfilaments involved in the transmembrane control of receptor mobility. We present electron microscopic evidence of structural alterations in microtubule and microfilament organization in anesthetic-treated cells, together with data on changes in the responsiveness of anesthetic-treated cells to drugs that act on microtubules and/or microfilaments. This evidence supports the proposal that anesthetics affect the organization of cytoskeletal components or their plasma membrane attachment points. The effects of local anesthetics on ligand-induced redistribution of membrane receptors in both 3T3 cells and lymphocytes can be duplicated by treating cells with colchicine (or Vinca alkaloids) together with cytochalasin B. We propose that the participation of membrane-associated microtubules and microfilaments in the transmembrane control of receptor mobility is such that microtubules and microfilaments play opposing roles in regulating the mobility and topography of cell surface receptors.
A theorem on the Schwartz space of a reductive Lie group
Authors: Arthur James
Published: May 2006

The purpose of this paper is to define the Fourier transform of an arbitrary tempered distribution on a reductive Lie group. To this end we define a topological vector space, [unk](
Ĝ
), in terms of the classes of irreducible unitary representations of
G
, which plays role of a dual Schwartz space. Our main theorem then asserts that the usual
L
2
Fourier transform, when restricted to functions in the Schwartz space, [unk](
G
) defined by Harish-Chandra, provides a topological isomorphism from [unk](
G
) onto [unk](
Ĝ
).
How ribosomes select initiator regions in mRNA: base pair formation between the 3' terminus of 16S rRNA and the mRNA during initiation of protein synthesis in Escherichia coli.
Authors: Steitz J A , Jakes K
Published: May 2006

Initiation complexes formed by E. coli ribosomes in the presence of 32P-labeled A protein initiator region from R17 bacteriophage Rna have been treated with colicin E3 and disassembled by exposure to 1% sodium dodecyl sulfate. Electrophoresis on 9% polyacrylamide gels reveals a dissociable complex containing the 30-nucleotide-long messenger fragment and the 50-nucleotide-long colicin fragment, which arises from the 3' terminus of the 16S RNA. The complex is a pure RNA-RNA hybird; it is apparently maintained by a seven-base complementarity between the two RNA fragments. Detection of this mRNA-rRNA complex strongly supports the hypothesis that during the initiation step of protein biosynthesis the 3' end of 16S RNA base pairs with the polypurine stretch common to initiator regions in E. coli and bacteriophage mRNAs. The implications of our findings with respect to the molecular mechanism of initiation site selection and mRNA binding to ribosomes, the role of rRNA in ribosome function, and species specificity in translation are explored.
A method for the isolation of specific tRNA precursors.
Authors: Vögeli G , Grosjean H , Söll D
Published: May 2006

tRNA affinity chromatography, based on complex formation between tRNAs with complementary anticodons, has been applied to the isolation of specific tRNA precursors. When [32P]RNA, isolated from an Escherichia coli strain containing a thermolabile ribonuclease P, was chromatographed on resin-bound yeast phenylalanine tRNA, precursor tRNAGlu (possessing the complementary anticodon) was specifically retained. Likewise, precursor tRNAPhe was isolated from a column of resin-bound E. coli glutamate tRNA. Both precursor tRNAs isolated were monomeric and may be processed products of an originally larger RNA precursor. Both tRNA precursors contain additional nucleotides beyond the 5'-end of the mature tRNA and have all modified bases found in mature tRNA. The method can be extended to isolate other tRNA precursors by affinity chromatography with different tRNAs. Since the principle of complementary anticodon interaction is not restricted to any particular organism, specific precursor tRNAs from other sources may also be isolated in this way.
Histone gene arrangement in the sea urchin, Strongylocentrotus purpuratus.
Authors: Weinberg E S , Overton G C , Shutt R H , Reeder R H
Published: May 2006

The DNA coding for histones from Strongylocentrotus purpuratus, purified up to 100-fold with the use of Hg+2-CS2-SO4 and actinomycin-CsC1 equilibrium density gradients, has been used to study the clustering of genes coding for different histones and the size of the repeating multigene cluster. When digested with EcoRI restriction endonuclease, the histone DNA is identified in two classes of fragments with molecular weights of 1.15 X 106 and 2.8 X 106, whereas after treatment of the DNA with HindIII restriction endonuclease, histone gene sequences can be identified only in a fragment of 3.95 X 106. Treatment of the DNA with both enzymes simultaneously shows that there is a HindIII site within the smaller EcoRI fragment. Partial digests with HindIII give fragment sizes that appear to be simple multiples of a 3.95 X 106 repeat. Individual histone mRNAs all hybridize to the 3.95 X 106 fragment but only to one or the other EcoRI fragments. The evidence strongly suggests a repeating unit of 3.95 X 106 containing the genes for most, if not all, the histonrs.
X-ray fiber diffraction evidence for neighbor exclusion binding of a platinum metallointercalation reagent to DNA.
Authors: Bond P J , Langridge R , Jennette K W , Lippard S J
Published: May 2006

Good quality x-ray diffraction patterns have been obtained of polycrystalline fibers containing 2-hydroxyethanethiolato(2,2'2"-terpyridine)platinum(II) bound to calf thymus DNA by intercalation. The photographs strongly support the neighbor exclusion binding model in which electron-dense platinum atoms are regularly distributed at 10.2 A intervals, every other interbase pair site.
Association of a cyclic AMP-dependent protein kinase with a purified translational inhibitor isolated from hemin-deficient rabbit reticulocyte lysates.
Authors: Levin D H , Ranu R S , Ernst V , Fifer M A , London L M
Published: May 2006

In the absence of added hemin, protein synthesis in rabbit reticulocyte lysates proceeds at maximal linear rates for several minutes and then ceases abruptly. Inhibition involves the action of a translational inhibitor whose formation is regulated by hemin. Addition of the isolated inhibitor to hemin-supplemented lysates produces an inhibition of protein chain initiation similar to that observed in heme-deficiency. The inhibitor has been purified over 300-fold and contains a protein kinase activity that copurifies with the inhibitory function. With calf thymus histone II as the phosphate receptor, the inhibitor-associated protein kinase requires ATP as the phosphorylating agent. Cycle AMP stimulates kinase activity 5- to 8-fold; the concentration of cycle AMP required for halfmaximal activity is 4 X 10-8 M. Preincubation of the inhibitor in the presence of cyclic AMP significantly reduces cyclic AMP-dependent phosphorylation and inhibitory activity. The corresponding protein kinase activity from hemin-supplemented lysates displays reduced cyclic AMP-dependency and little or no inhibitory activity. These findings suggest that the protein kinase activity associated with the purified translational inhibitor is involved in the mechanism of inhibition of initiation observed in hemedeficient reticulocyte lysates.
Search for nucleic acid sequences complementary to a murine oncornaviral genome in poly(A)-rich RNA of human leukemic cells.
Authors: Larsen C J , Marty M , Hamelin R , Peries J , Boiron M , Tavitian A
Published: May 2006

The presence of viral-like sequences in the RNA of various types of leukemic cells was investigated by hybridizing cellular poly(A)-containing RNA with cDNA synthesized in an endogenous system of purified Moloney murine sarcoma virus [M-MSV-(MLV)]. Poly(A)-RNA-cDNA hybrids were detected by assaying their resistance to S1 nuclease. Hybrids were found in 22 out of the 46 leukemias that were tested. None of the controls, including material obtained from buffy coats, bone marrow cells, and a continuous human cell line, was positive. Positive cases were found in all the different categories of leukemias with the exception of chronic myelogenous leukemias. There was no definite corelation between the category of leukemia and positivity. A few cases contained a very high proportion of poly(A)-RNA-cDNA hybrid.
Procollagen: biological scission of amino and carboxyl extension peptides.
Authors: Fessler L I , Morris N P , Fessler J H
Published: May 2006

Procollagen, the triple-stranded precursor of chick embryo skull bone collagen, contains two pro alpha1 and one pro alpha2 chains. We find that each of these is a collagen chain with both an NH2-terminal and a COOH-terminal extension peptide. The NH2-peptide of pro alpha1 contains cysteine and differs from the NH2-peptide of pro alpha2. The three NH2-peptides are cut off, giving a disulfide-linked intermediate, named altered procollagen; then the disulfide-linked COOH-peptides, which contain cysteine and tryptophan, are cut off, leaving collagen. Procollagen, altered procollagen, and COOH-peptide were isolated. Collagenase digestion of procollagen gave both NH2- and COOH-peptides, while altered procollagen gave only COOH-peptides. The following results of sequential, in vitro labeling at 37 degrees and of specific cleavage of procollagen proved the structure: [(NH2-peptide)-collagen-(COOH-peptide)]3 with interstrand S-S links between only the COOH-peptides. (i) The COOH-peptides of pro alpha chains were labeled with [3H]proline before the remainders of the chains; (ii) [35S]cysteine appeared in the COOH-peptides of completed covalent molecules 5 min earlier than in the NH2-peptides; (iii) tadpole tail collagenase, which cuts native collagen into triple-stranded 3/4 pieces containing the NH2 termini and 1/4 pieces containing the COOH ends, cuts procollagen into 3/4 pieces with NH2-peptides attached and 1/4 pieces attached to the disulfide-linked COOH-peptides. The COOH-peptides of pro alpha 1 and pro alpha2 were labeled in a 2:1 ratio at 4 min, indicating simultaneous translation of pro alpha1 and pro alpha2.
Neuronal properties of hybrid neuroblastoma X sympathetic ganglion cells.
Authors: Greene L A , Shain W , Chalazonitis A , Breakfield X , Minna J , Coon H G , Nirenberg M
Published: May 2006

Clonal mouse neuroblastoma cells without tyrosine 3-monooxygenase [EC 1.14.16.2; tyrosine hydroxylase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating)] activity were fused with normal cells from embryonic mouse sympathetic ganglia. One of the 37 hybrid cell lines obtained possesses high tyrosine 3-monooxygenase activity and synthesizes dopamine. These cells also have excitable membranes and generate action potentials in response to electrical stimuli. Thus hybrid cells, generated by fusion of neuroblastoma cells with normal cells from the nervous system, can acquire neural properties not found with the parental neuroblastoma cells.
Apoprotein stability and lipid-protein interactions in human plasma high density lipoproteins.
Authors: Tall A R , Small D M , Shipley G G , Lees R S
Published: May 2006

Temperature-dependent conformational changes of the principal apoprotein of human plasma high density lipoprotein (HDL), apoA-I, have been studied in the isolated apoprotein, in complexes of apoprotein with phospholipid, and in intact HDL. Differential scanning calorimetry shows that in solution apoA-I undergoes a reversible, two-state thermal denaturation (midpoint temperature 54 degrees). The enthalpy (2.4 cal/g)(10.0 J/g) and specific heat change (0.08 cal/degrees C per g)(0.33 J/degrees C per g) associated with the denaturation were used to calculate the free energy difference (deltaG) between native and unfolded apoA-I at 37 degrees. DeltaG (2.4 kcal/mol)(10.0 kJ/mol) is less than that of other globular proteins (typically 8-14 kcal/mol)(33-59 kJ/mol), indicating that at 37 degrees native apoA-I has a loosely folded conformation. Turbidity studies show that apoA-I is able to solubilize phospholipid in its native but not in its denatured form. Mixtures of apo-HDL (the total apoprotein of HDL) or apoA-I with dimyristoyl lecithin show a thermal transition at about 85 degrees not present in the lecithin or the apoprotein alone, which indicates that the native conformation of the apoprotein is stabilized by phospholipid. Scanning calorimetry of intact HDL shows a high-temperature endotherm associated with disruption of the HDL particle, suggesting that in HDL the conformation of apoA-I is also stabilized by interaction with lipid. The loosely folded conformation of native, uncomplexed apoA-I may be especially adapted to the binding of lipid, since this process may involve both hydrophobic sites on the surface of the protein and concealed apolar amino acid residues that are exposed by a cooperative, low energy unfolding process.
Electron microscopic observations on the meiotic karyotype of diploid and tetraploid Saccharomyces cerevisiae.
Authors: Byers B , Goetsch L
Published: May 2006

Certain strains of Saccharomyces cerevisiae contain visible segments of synaptonemal complex which are apparent components of bivalents in pachytene of meiotic prophase. The synaptonemal complex has the typical width in the frontal plane but is unusually thin in the sagittal plane, thus accounting for its poor visibility. Amorphous densities situated adjacent to the central element occur at intervals suggesting their coincidence with sites of crossing over. Reconstruction of the synaptonemal complex from serial sections has permitted karyotypic analysis. The number of segments of synaptonemal complex and the distribution of their legths is consistent with the genetic map. Two, possibly three, segments enter the nucleolus as if bearing sequences encoding ribosomal RNA. Reconstruction of tetraploid nuclei reveals an approximate doubling of the diploid chromosome number and confirms the pattern of nucleolar entry. Quadrivalent pairing is evident between the pairs of synaptonemal complex segments in the tetraploid nuclei.
Resonance raman spectra of manganese (III) tetraphenylporphin halides.
Authors: Gaughan R R , Shriver D F , Boucher L J
Published: May 2006

Unique resonance Raman spectra were obtained when manganese(III) tetraphenylporphin halides in noncoordinating solvents were illuminated by laser frequencies around 500 nm. Of particular interest is the observation of a feature that is sensitive to the nature of the axial ligand. This feature disappears when the coordinating solvent pyridine is employed, and it, therefore, appears to be diagnostic of the manganese coordination number.
Blue dextran-sepharose: an affinity column for the dinucleotide fold in proteins.
Authors: Thompson S T , Cass K H , Stellwagen E
Published: May 2006

A procedure is described to utilize blue dextran-Sepharose as an affinity chromatographic column specific for the super-secondary structure called the dinucleotide fold, which forms the binding sites for substrates and effectors on a wide range of proteins. The procedure can be used to identify proteins, either purified or in crude cellular extracts, that possess the dinucleotide fold and to significantly improve the purification procedures for those proteins that possess the fold.
Interaction of poly(A) and mRNA with eukaryotic initiator met-tRNA-f binding factor: identification of this activity on reticulocyte ribonucleic acid protein particles.
Authors: Hellerman J G , Shafritz D A
Published: May 2006

Messenger ribonucleoprotein particles (mRNPs) have been isolated from rabbit reticulocyte polysomes. One of the proteins of the mRNP complex has many properties of a specific eukaryotic initiation factor, the soluble Met-tRNA-f binding protein. A purified preparation of this factor, in addition to binding Met-tRNA-f, binds poly(A) and globin mRNA. The binding of these substrates is greater than that obtained with other natural or artificial polyribonucleotides. The mRNP fraction also binds poly(A) and Met-tRNA-f. Since the factor which binds initiator tRNA also binds poly(A) and mRNA, and this activity can be found on mRNPs, there may be a relationship between initiator tRNA binding and messenger binding in early events of eukaryotic initiation.
Separation of transfer ribonucleic acid by sepharose chromatography using reverse salt gradients.
Authors: Holmes W M , Hurd R E , Reid B R , Rimerman R A , Hatfield G W
Published: May 2006

The transfer ribonucleic acids of Escherichia coli bind to unsubstituted Sepharose in the presence of high concentrations of ammonium sulfate at pH 4.5. Transfer RNA species are eluted individually from the Sepharose by a gradient from high to low concentrations of ammonium sulfate; leucine tRNA is fractionated into five isoaccepting species. The order of elution of these isoaccepting species differs from that seen with reverse phase chromatography. By means of only these two procedures, one isoaccepting species of leucine tRNA can be purified to apparent homogeneity. Isoaccepting tRNA species for 9 amino acids have been resolved. This established the general utility of this chromatographic system for the separation and purification of specific isoaccepting transfer RNAs.
Chromatin directed transcription of 5S and tRNA genes.
Authors: Marzluff W F , Huang R C
Published: May 2006

Chromatin prepared by gentle methods from mouse myeloma cells retained its ability to synthesize RNA using bound endogenous RNA polymerase (RNA nucleotidyltransferase; nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6). The transcription resembles that observed in vivo in several respects. The low-molecular-weight RNA species 5S RNA and the 4.5S precursor to 4S RNA, are transcribed accurately and transcription is reinitiated continually in vitro. Their synthesis was not inhibited by alpha-amanitin (1 mug/ml) as was found previously for these species in isolated nuclei.
Genetic heterogeneity in familial hypercholesterolemia: evidence for two different mutations affecting functions of low-density lipoprotein receptor.
Authors: Goldstein J L , Dana S E , Brunschede G Y , Brown M S
Published: May 2006

Studies in cultured fibroblasts from patients with the clinical syndrome of homozygous familial hypercholesterolemia have disclosed two different mutations affecting the functions of the low density lipoprotein receptor. One of these mutations, described previously, results in a functionless receptor that does not bind low density lipoproteins. In the cells of six patients who appear to be homozygous for this mutant allele, i.e., receptor-negative homozygotes, low density lipoproteins neither suppress hydroxymethylgultaryl-CoA reductase (NADPH) [mevalonate:NADP+ oxidoreductase (CoA-acylating) EC 1.1.1.34] activity nor stimulate cellular cholesterol esterification, even when examined in the presence of concentrations of lipoprotein 500 times higher than those cells. The second type of mutation, described herein, results in a receptor that has a reduced but not absent function. Fibroblasts from three subjects who possess this mutation, i.e., receptor-defective homozygotes, show partial suppression of the same enzyme activity and a detectable increase in cholesterol esterification capacity in the presence of high levels of low density lipoproteins. It was calculated that their degree of function could be achieved if they possessed only about 10% of the normal binding of low density lipoprotein. This level of binding was too low to be reliably detected by the 125-I-labeled low density lipoprotein binding assay. The finding of a second class of mutant cells in which a defect in low density lipoprotein binding is associated with simultaneous defects in both suppression of hydroxymethylglutaryl-CoA reductase activity and stimulation of cholesterol ester formation provides further evidence for the coordinate control of these two processes by the low density lipoprotein receptor.
Hemoglobin synthesis in somatic cell hybrids: globin gene expression in hybrids between mouse erythroleukemia and human marrow cells or fibroblasts.
Authors: Deisseroth A , Burk R , Picciano D , Anderson W F , Nienhuis A , Minna J
Published: May 2006

Somatic cell hybrids were generated by fusion of mouse erythroleukemia cells either to mouse L cells (B82), human fibroblasts (W1-18 VA2), or human marrow fractions enriched in erythroblasts. The hybrid cells were examined for globin gene expression by benzidine staining to detect cytoplasmic hemoglobin, and by molecular hybridization of cellular RNA to globin complementary DNA (cDNA) to detect globin messenger RNA (MRNA). The fibroblast (human or mouse) times erythroleukemia cell hybrids grown in monolayer retained most of the chromosomes of each parent. Neither cytoplasmic hemoglobin nor globin mRNA was detected in dimethylsulfoxide-treated fibroblast times erythroleukemia hybrid cells, indicating extinction of hemoglobin synthesis prior to the formation of cytoplasmic mRNA. The human marrow times mouse erythroleukemia hybrid cells grown in suspension culture contained only a few human chromosomes and exhibited low levels of hemoglobin synthesis which were amplified by 2% dimethylsulfoxide. Mouse (but not human) globin mRNA was demonstrated in these hybrid cells. The results suggest that somatic cell hybrids may be useful in searching for genetic factors which regulate activity of the globin genes.
Affinity chromatography of viral DNA polymerases on pyran-sepharose.
Authors: Chirikjian J G , Rye L , Papas T S
Published: May 2006

Pyran covalently linked to cyanogen bromide-activated Sepharose has been shown to be an effective affinity matrix for several viral DNA polymerases. Differential salt elution of viral compared with cellular polymerases, as well as substrate elution, suggests the affinity nature for the matrix. Unlike some other affinity systems described, pyran-Sepharose is totally resistant to nuclease digestion and is stable at 4 degrees for several months. DNA polymerases isolated from several viruses by detergent treatment were recovered in good yield. Analysis of iodinated proteins by sodium dodecyl sulfate-gel electrophoresis revealed that the DNA polymerase of avian myeloblastosis virus found in crude preparations of the virus could be purified nearly to homogeneity by a single passage through the column. These results suggest that pyran-Sepharose is an effective affinity column that is potentially adaptable as part of a general purification procedure for viral DNA polymerases.
Differentiation of population of peripheral blood lymphocytes into cells bearing sheep erythrocyte receptors in vitro by human thymic extract.
Authors: Vogel J E , Incefy G S , Good R A
Published: May 2006

A small population of human marrow cells has been shown to be differentiated in vitro by thymic extract into cells bearing T-lymphocyte (thymus-derived lymphocyte) characteristics. By a similar method, the differentiation of human peripheral blood lymphocytes has been studied. A discontinuous gradient of bovine serum albumin was used to isolate lymphocytes into four layers and cells from layers I and III demonstrated the greatest potential for differentiation by human thymic extract. Appearance of T-lymphocyte characteristics was recognized by the spontaneous E-rosette technique with sheep erythrocytes. Ability of human marrow cells to be differentiated under the influence of human thymic extract was abolished by specific inhibitors of nucleic acid synthesis, however, had no inhibitory effect on the maturation of peripheral blood lymphocytes during a 2 hr incubation with human thymic extract but puromycin, an inhibitor of protein synthesis, abolished this differentiative step in cells of layer I. It is suggested from these studies that many of the cells in peripheral blood that are differentiable by thymic extract are at a stage of maturation more advanced than those in human marrow that are also differentiable by thymic extract.
X
and
Y
Operators for General Linear Transport Processes
Authors: Casti J.
Published: May 2006

This note presents the derivation of generalized Ambartsumian-Chandrasekhar
X
and
Y
functions for stationary transfer in a plane-parallel slab. An algebraic formula relating these functions to the usual reflection function is also presented, together with the appropriate generalization of the Chandrasekhar
H
-equations for the semi-infinite medium. The planetary problem will also be briefly discussed.
Variability of three-dimensional structure in immunoglobulins.
Authors: Padlan E A , Davies D R
Published: May 2006

A comparison of various variable immunoglobulin domains demonstrates that structural variability parallels the observed frequency of amino-acid substitutions. The similarity of the structural frameworks is in good agreement with the evolutionary relationships of the chains as derived from sequence analysis.
Replicative intermediates of colicin E1 plasmid DNA in minicells.
Authors: Oka A , Inselburg J
Published: May 2006

Pulse-labeled colicin E1 plasmid (Col E1) DNA in minicells was examined to characterize replicating molecules. Replication of Col E1 DNA principally occurred in covalently closed molecules and involved the synthesis of variable length single-stranded DNA fragments that were dissociable from the template DNA and ultimately incorporated into the completely replicated molecules. RNA was found to be associated with some of these newly synthesized fragments. Replicating molecules containing different size displacement loops were observed by electron microscopy.
Intermediates in the biosynthesis of double-stranded ribonucleic acids of bacteriophage phi 6.
Authors: Coplin D L , Van Etten J L , Koski R K , Vidaver A K
Published: May 2006

Pseudomonas phaseolicola infected with bacteriophage phi 6 synthesized all three viral double-stranded RNA segments, three single-stranded RNAs, and three replicative intermediate-like RNAs in the presence of rifampin. The single-stranded RNA intermediates sedimented and electrophoresed along with melted viral double-stranded RNA, annealed with melted viral double-stranded RNA, and were transient in nature. The relative amounts of the single-stranded RNA intermediates varied during the infection cycle and were altered in the presence of chloramphenicol. The replicative intermediate-like RNAs sedimented faster than double-stranded RNA, failed to enter 2.5% polyacrylamide gels, eluted with double-stranded RNA from a CF-11 cellulose column, were precipitated with single-stranded RNA in 2 M LiC1, and yielded three genome-size pieces of double-stranded RNA upon digestion with RNase. These results are consistent with the hypothesis that complementary strands of the phi 6 double-stranded RNAs are synthesized asynchronously during the infection cycle.
Paired moving charge model of energy coupling. III. Intrinsic ionophores in energy coupling systems.
Authors: Green D E , Blondin G , Kessler R , Southard J H
Published: May 2006

The experimental basis for the postulated role of intrinsic ionophores in mitochondrial ion transport and energy coupling is summarized. Intrinsic ionophores appear to be linked to, or contained within, specific ionophoroproteins localized in the inner membrane, and the isolation of these ionophores requires their release from the ionophoroproteins. At least ten different species of ionophores have been isolated from the mitochondrion, five of which have been wholly or in part chemically identified. Intrinsic ionophores have been implicated in the activation of inorganic phosphate in ATP synthesis and hydrolysis, and in the contol of the coupling modes. The presence of ionophores in soluble proteins such as troponin and in ATP-energized kinases has been demonstrated.
Thermochemotherapy: synergism between hyperthermia (42-43 degrees) and adriamycin (of bleomycin) in mammalian cell inactivation.
Authors: Hahn G M , Braun J , Har-Kedar I
Published: May 2006

The sensitivity of cells exposed in vitro to the antibiotics bleomycin or adriamycin is only mildly increased at 41 degrees over that seen at 37 degrees. However, at 43 degrees a marked synergism between the effects of hyperthermia and drug is observed. This synergism can also be demonstrated to occur in solid tumors in vivo. Cells after bleomycin exposure at 37 degrees repair potentially lethal damage, and 43 degrees inhibits this repair. This inhibition may in part account also for the observed sensitization of the cells to bleomycin, but not to adriamycin, since for the latter no repair can be demonstrated. However, fluorescence measurements show that at 43 degrees much more adriamycin is able to enter the cells than at 37 degrees. The possible implications of the results for cancer treatment are discussed.
Free radicals formed by exposure of pyrimidine solids to sodium atoms: an electron spin resonance study.
Authors: Johnson G A
Published: May 2006

Sodium atoms have been deposited on various pyrimidine powders under high vacuum at 77 degrees K and the electron spin resonance spectra of the resulting free radicals have been observed. Generally, the spectra show that the electron of the Na goes into a molecular orbital of the pyrimidine ring and the Na+ ions become attached to a carbonyl oxygen of the resulting pyrimidine anion. In 5-fluorouracil and 5-chlorouracil, however, the halogen is evidently abstracted by the Na to form NaF or NaC1 and the neutral uracil radical. Thymine shows evidence for H-addition radicals as well as the Na+-[thymine]-complex. The H source for the addition radicals may be an H-2-0 impurity in the sample, with which the Na atoms combine to release the H atoms. In addition to a resonance with g equals 2.00 from the pyrimidine anion radical, broad resonances with g greater than 2 were observed for 5-bromouracil, 5-chlorouracil and 5-iodouracil, as well as for alloxan and cytosine. These resonances, generally unstable at room temperature, are believed to arise from electrons trapped in interstitial sties or vacancies in the lattice.
Genetic evidence for an additional function of phage T4 gene 32 protein: interaction with ligase.
Authors: Mosig G , Breschkin A M
Published: May 2006

Gene 32 of bacteriophage T4 is essential for DNA replication, recombination, and repair. In an attempt to clarify the role of the corresponding gene product, we have looked for mutations that specifically inactivate one but not all of its functions and for compensating suppressor mutations in other genes. Here we describe a gene 32 ts mutant that does not produce progeny, but in contrast to an am mutant investigated by others, is capable of some primary and secondary DNA replication and of forming "joint" recombinational intermediates after infection of Escherichia coli B at the restrictive temperature. However, parental and progeny DNA strands are not ligated to covalently linked "recombinant" molecules, and single strands of vegetative DNA do not exceed unit length. Progeny production as well as capacity for covalent linkage in this gene 32 ts mutant are partially restored by additional rII mutations. Suppression by rII depends on functioning host ligase [EC 6.5.1.2; poly(deoxyribonucleotide):poly(deoxyribonucleotide) ligase (AMP-forming, NMN-forming)]. This gene 32 ts mutation (unlike some others) in turn suppresses the characteristic plaque morphology of rII mutants. We conclude that gene 32 protein, in addition to its role in DNA replication and in the formation of "joint" recombinational intermediates, interacts with T4 ligase [EC 6.5.1.1; poly(deoxyribonucleotide):poly(deoxyribonucleotide) ligase (AMP-forming)] when recombining DNA strands are covalently linked. The protein of the mutant that we describe here is mainly defective in this interaction, thus inactivating T4 ligase in recombination. Suppressing rII mutations facilitate substitution of host ligase. There is suggestive evidence that these interactions occur at the membrane.
Hemoglobin interaction in sickle cell fibers. I: Theoretical approaches to the molecular contacts.
Authors: Levinthal C , Wodak S J , Kahn P , Dadivanian A K
Published: May 2006

Computerized molecular model building has been used to deduce the arrangement of sickle cell hemoglobin molecules (Hb-S) in the tubular fibers which form within sickling cells and in concentrated cell-free solutions of deoxygenated Hb-S. A "best" solution has been found which satisfies all of the reported properties of these fibers. In the proposed arrangement the contact between adjacent Hb-S molecules in the direction parallel to the fiber axis is primarily hydrophobic and in addition contains two salt bridges between the molecules. This contact would be disrupted with the Glu of Hb-A at the beta6 position instead of the Val of Hb-S, and it would not make a long fiber with oxygenated Hb-S. Residues in the A helix and the GH corner of the beta2 chain of one molecule are in contact with residues of the A, B, and E helices and the GH corner of the alpha1 chain of its neighbor. The intermolecular contact in the direction perpendicular to the fiber axis is mainly between the end of the E helix and the EF corner of the beta1 chain on the first molecule and the F helix and FG corner of the alpha2 chain of its neighbor. Some of the implications of these contacts are reported here, and others will be presented in subsequent papers.
Site specific recA--independent recombination between bacterial plasmids: involvement of palindromes at the recombinational loci.
Authors: Kopecko D J , Cohen S N
Published: May 2006

A recA-independent recombinational event is described which results in insertion of an entire plasmid genome at a unique site of another plasmid, and coincident excision of a precisely defined DNA segment originally present at the point of the insertion. The resulting recombinant molecules subsequently can undergo site-specific translocation of their component segments or inversion of their original DNA sequence orientation. The events observed entail nonreciprocal exchange of genetic material, and involve a discrete nucleotide sequences that is duplicated in rotationally symmetrical reverse orientation on plasmid DNA (i.e., inverted repeat; palindrome).