abstract：:We have shown that a scanning transmission electron microscope with a high brightness field emission source is capable of obtaining better than 3 A resolution using 30 to 40 keV electrons. Elastic dark field images of single atoms of uranium and mercury are shown which demonstrate this fact as determined by a modified...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Wall J,Langmore J,Isaacson M,Crewe AV

更新日期：1974-01-01 00:00:00

abstract：:Prolyl hydroxylase and other enzymes of collagen synthesis have been found in cloned cells, including epithelium, melanoma, liver, HeLa, pituitary, kidney, and neuroblastoma. The significance of collagen biosynthesis in nonfibroblastic cells lines is discussed. ...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Langness U,Udenfriend S

更新日期：1974-01-01 00:00:00

abstract：:The heterogeneous RNA of the HeLa cell nucleus contains short internal poly(A) sequences which, in contrast to the longer poly(A) sequences at the 3' ends, are not found in messenger RNA of the cytoplasm. A distinct origin for each of these homologous sequences is evident when the effects of actinomycin D and 3'-deoxy...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Nakazato H,Edmonds M,Kopp DW

更新日期：1974-01-01 00:00:00

abstract：:The regional structure of fibrinogen was considered in reference to the terminal plasmin-cleavage fragments, D and E. By two independent approaches, a yield of two D and two E fragments was determined and this established the presence of two D and two E regions in each fibrinogen molecule. Immunochemically, it was sho...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Plow EF,Edgington TS

更新日期：1974-01-01 00:00:00

abstract：:Certain chemical systems which differ greatly in many of their chemical properties may nevertheless exhibit stereochemically isomorphic behavior, i.e., they may be stereochemically correspondent. Two such systems are spirocyclic pentacoordinate molecules and molecules of the type Ar(2)ZX. The consequences of stereoche...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Gust D,Finocchiaro P,Mislow K

更新日期：1973-12-01 00:00:00

abstract：:Anaerobic beta-galactoside transport in whole cells and membrane vesicles from E. coli ML 308-225 is coupled to the oxidation of alpha-glycerol-P or D-lactate with fumarate as an electron acceptor. Alternatively, anaerobic beta-galactoside transport may be coupled to the oxidation of formate utilizing nitrate as elect...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Konings WN,Kaback HR

更新日期：1973-12-01 00:00:00

abstract：:Superoxide dismutase from chicken-liver mitochondria (manganese enzyme) and the two dismutases from Escherichia coli (manganese and iron enzymes) were analyzed through 29 cycles of automated Edman degradations. The high degree of homology among the amino-terminal sequences of these three dismutases corroborates their ...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Steinman HM,Hill RL

更新日期：1973-12-01 00:00:00

abstract：:We introduced radioactive precursors directly into identified neurons of Aplysia californica. [(3)H]-Choline and L-[(3)H]tryptophan were injected with pressure into nerve cell bodies to study synthesis of acetylcholine and serotonin. We confirmed the cholinergic nature of R2, L10, and L11, identified neurons of the ab...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Eisenstadt M,Goldman JE,Kandel ER,Koike H,Koester J,Schwartz JH

更新日期：1973-12-01 00:00:00

abstract：:Glucagon and insulin are first detectable at the onset of rat pancreas organogenesis. Initially, the specific activity of glucagon is approximately 100-fold higher than that of insulin. At this early stage, endocrine storage granules, similar to alpha granules, are identifiable in electron micrographs. The granule cha...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Rall LB,Pictet RL,Williams RH,Rutter WJ

更新日期：1973-12-01 00:00:00

abstract：:The receptor for acetylcholine was partially purified by affinity chromatography of an extract in Triton X-100 of membrane fragments from electric tissue. The receptor was assayed, after its reduction with dithiothreitol, by reaction with the affinity-alkylating agent, [methyl-(3)H]4-(N-maleimido)-benzyltrimethylammon...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Karlin A,Cowburn D

更新日期：1973-12-01 00:00:00

abstract：:In regulating gene expression in mammalian tissues, steroid hormones bind to cytoplasmic receptors and the resulting complex associates with the nucleus. In an attempt to study this nuclear association under more precisely controlled conditions, we examined the binding of receptor-[(3)H]steroid complexes to isolated n...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Higgins SJ,Rousseau GG,Baxter JD,Tomkins GM

更新日期：1973-12-01 00:00:00

abstract：:The RNA synthesized in vitro by the virion-associated RNA-instructed RNA polymerase of purified vesicular stomatitis virus contains polyadenylate sequences. These have been demonstrated by their partial resistance to pancreatic and T(1) ribonucleases and their capacity to bind to poly(U) filters and oligo(dT)-cellulos...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Banerjee AK,Rhodes DP

更新日期：1973-12-01 00:00:00

abstract：:The magnetic circular dichroism of benzene and indole derivatives was measured down to 190 nM. The following pairs of molecules have magnetic circular dichroisms of the opposite sign in the B(2u) absorption region: aniline and benzonitrile, indene and indoline, indole and 4-aminoindole, and 4-aminoindole and 5-aminoin...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Miles DW,Eyring H

更新日期：1973-12-01 00:00:00

abstract：:The ultrastructure of the crystalline ferric mineral that forms the central core of ferritin macro-molecules has been examined by means of ultrahigh resolution electron microscopy at 100 kV. Very high magnification dark-field images reveal the presence of either a single large crystal or several smaller crystallites w...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Massover WH,Cowley JM

更新日期：1973-12-01 00:00:00

abstract：:To investigate how cell population density influences the intracellular concentration of cyclic AMP we have measured adenylate cyclase and cyclic AMP phosphodiesterase activities and cyclic AMP levels at various stages of cell density in normal rat-kidney (NRK) cells, which exhibit contact-inhibition of growth, and in...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Anderson WB,Russell TR,Carchman RA,Pastan I

更新日期：1973-12-01 00:00:00

abstract：:The possible role of guanosine 5'-triphosphate,3'-diphosphate (pppGpp) in protein synthesis by Escherichia coli ribosomes and protein factors was examined. Although pppGpp could effectively substitute for GTP in reactions catalyzed by initiation factor 2 (ribosomal binding of fMet-tRNA and formation of N-formylmethion...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Hamel E,Cashel M

更新日期：1973-11-01 00:00:00

abstract：:The growth or decay of population of a single species interacting with a large number of other species (or environment) according to the Volterra-Lotka model is investigated. When the environment is initially very close to its equilibrium level, the growth of a single species follows a generalized Verhulst law, contai...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Zwanzig R

更新日期：1973-11-01 00:00:00

abstract：:The circular dichroism of hypothetical, water-filled, spherical shells, 75-3500 nm in radius, with walls 7.5 nm thick, composed of poly(L-lysine) in various conformational proportions, and suspended in water, were computed from the known optical properties of this polypeptide by classical general light-scattering theo...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Wallach DF,Low DA,Bertland AV

更新日期：1973-11-01 00:00:00

abstract：:The DNA-containing Epstein-Barr herpesvirus has been implicated in the etiology of Burkitt's lymphoma, a malignant tumor of children in Africa. Recently, however, particles possessing four biochemical characteristics of RNA tumor viruses have also been identified in these tumors. The fact that both types of viruses ar...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Peters WP,Kufe D,Schlom J,Frankel JW,Prickett CO,Groupé V,Spiegelman S

更新日期：1973-11-01 00:00:00

abstract：:Formation of duplex DNA from varphiX174 single-stranded DNA by extracts of E. coli was previously shown to require the gene product of dna B. Using as an assay the stimulation of varphiX174 DNA-dependent synthesis in inactivated extracts of dna B temperature-sensitive cells, we purified the dna B gene product from wil...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Wright M,Wickner S,Hurwitz J

更新日期：1973-11-01 00:00:00

abstract：:Glutamine-dependent carbamylphosphate synthetase (Escherichia coli) is composed of a heavy subunit (molecular weight about 130,000) and a light subunit (molecular weight about 42,000), which can be separated with retention of catalytic activities. The separated heavy subunit can catalyze activation of CO(2) by ATP and...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Trotta PP,Wellner VP,Pinkus LM,Meister A

更新日期：1973-10-01 00:00:00

abstract：:It was shown in an earlier paper how to connect, in principle, the biochemical states of a cross-bridge with the mechanics of muscular contraction, by the methods of statistical mechanics. The treatment applies to cross-bridges that are able to interact with only one actin site at a time. The present paper shows that ...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Hill TL

更新日期：1973-10-01 00:00:00

abstract：:A mol of creatine kinase (EC 2.7.3.2), an enzyme with two identical subunits can be titrated very rapidly and stoichiometrically with 2 mol of 2-chloromercuri-4-nitrophenol, an environmentally sensitive chromophoric probe specific for thiols. Chemical modification does not inactivate the enzyme nor can the reaction be...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Quiocho FE,Thomson JW

更新日期：1973-10-01 00:00:00

abstract：:Chick calvaria labeled in vitro contain a triple-stranded collagen precursor that contains two pro alpha1 and one pro alpha2 chains. All chains contain cystine and are linked by S-S bonds. Ultracentrifugal analysis was used to measure the relative size of the disulfide-linked units. It is proposed that the S-S links h...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Fessler LI,Burgeson RE,Morris NP,Fessler JH

更新日期：1973-10-01 00:00:00

abstract：:A technique is described for isolation of plasmid DNA in closed and open circular double-stranded forms from bacterial cells, by use of ATP-dependent deoxyribonuclease purified from Micrococcus luteus. This DNase, acting only upon linear DNA molecules, degrades all bacterial chromosomal DNA extracted in the linear for...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Mukai T,Matsubara K,Takagi Y

更新日期：1973-10-01 00:00:00

abstract：:RNA from noninfectious virions produced by two established clonal lines of sarcoma positive-leukemia negative (S+L-)-transformed 3T3 cells has been characterized. RNA from virions or nucleoids of S+L--(C243) cells consisted of three to four sizes: +/-44 S (6%), 28 S (17%), 18 S (38%), and <18 S (39%). 28S virion RNA c...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Phillips LA,Hollis VW Jr,Bassin RH,Fischinger PJ

更新日期：1973-10-01 00:00:00

abstract：:Surface proteins of mouse thymus and spleen cells were radioiodinated with lactoperoxidase. After solubilization, the labeled proteins were precipitated by antibodies directed against mouse immunoglobulin chains; the precipitates were analyzed by radioautography after Na dodecyl sulfate-gel electrophoresis. Radioactiv...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Lisowska-Bernstein B,Rinuy A,Vassalli P

更新日期：1973-10-01 00:00:00

abstract：:To determine whether bacterial ribosomes recognize a distinguishing feature in the immediate vicinity of actual initiator codons or are directed to these sites through involvement of other portion(s) of the mRNA molecule, the interaction between ribosomes and defined (32)P-labeled initiator fragments from R17 RNA was ...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Steitz JA

更新日期：1973-09-01 00:00:00

abstract：:A type of heritable cellular change, known as habituation, occurs spontaneously in plant tissue and cell culture. This phenomenon is characterized by a newly acquired capacity of plant cells to produce growth regulatory substances. Using cloned lines of tobacco pith parenchyma cells, we demonstrated that a newly acqui...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Binns A,Meins F

更新日期：1973-09-01 00:00:00

abstract：:An assay has been developed to test the hypothesis that neurons from a limited area of the retina will adhere preferentially to that part of the optic tectum near their normal synaptic termini. The method measures the adherence of (32)P-labeled cell bodies from either the dorsal or ventral half of the neural retina of...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Barbera AJ,Marchase RB,Roth S

更新日期：1973-09-01 00:00:00

abstract：:Guanosine tetraphosphate, recently discovered to mediate the regulatory relationship between protein synthesis and RNA accumulation in various bacteria, has been synthesized in vitro in large quantities and analyzed by natural-abundance (13)C nuclear magnetic resonance spectroscopy in order to confirm its structure an...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Que L Jr,Willie GR,Cashel M,Bodley JW,Gray GR

更新日期：1973-09-01 00:00:00

abstract：:Ultraviolet photosensitivity of the single-stranded forms of poly(A) and poly(dA) is compared. In contrast to poly(A), poly(dA) is rather sensitive to ultraviolet irradiation. Relatively low doses of ultraviolet light lead to characteristic changes of the ultraviolet and circular dichroism spectra of poly(dA), suggest...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Pörschke D

更新日期：1973-09-01 00:00:00

abstract：:Results are reported showing that pituitary extracts stimulate growth of 3T3 cells, an established line of mouse fibroblast. Cells were cultured in medium containing an organic buffer (HEPES; N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid), which increases the serum requirement for cell growth. The pituitary grow...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Armelin HA

更新日期：1973-09-01 00:00:00

abstract：:Reactions of a membrane-bound multienzyme complex (electron-transport chain of rat-liver microsomes) suspended in aqueous-organic solvent used as antifreeze at temperatures below 0 degrees were studied. In the presence of a relatively high concentration of ethylene glycol, electron transfer can still be observed and s...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Debey P,Balny C,Douzou P

更新日期：1973-09-01 00:00:00

abstract：:The primary structure of about half of the protein chain of yeast alcohol dehydrogenase has been determined and compared with the amino-acid sequences of other dehydrogenases. The enzyme is found to be distantly related to horse-liver alcohol dehydrogenase, although these two proteins have different quaternary structu...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Jörnvall H

更新日期：1973-08-01 00:00:00

abstract：:In order to retain in an in situ system the control mechanisms involved in synthesis of bacteriophage T4 DNA, infected cells were made permeable to nucleotides by plasmolysis with concentrated sucrose. Such preparations use exogenous deoxyribonucleotides to synthesize T4 phage DNA. As has been observed with in vivo st...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Wovcha MG,Tomich PK,Chiu CS,Greenberg GR

更新日期：1973-08-01 00:00:00

abstract：:Release of formylmethionine from the reticulocyte ribosomal substrate, f[(3)H]Met-tRNA.ribosome, is promoted by reticulocyte release factor (RF). The initial rate of this reaction is stimulated by GTP but inhibited by GDPCP. Formation of an RF.UA[(3)H]A(2).ribosome complex is a measure of the binding of reticulocyte R...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Tate WP,Beaudet AL,Caskey CT

更新日期：1973-08-01 00:00:00

abstract：:Column chromatography on (dT)(12-18)-cellulose was used to detect and isolate a novel DNA polymerase activity from human breast tumor cell line HBT-3. The new enzyme is similar to those of mammalian RNA tumor viruses in its molecular size, preference for poly(A).(dT)(12-18) as compared to either poly(dA).(dT)(12-18) o...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Gerwin BI,Bassin RH

更新日期：1973-08-01 00:00:00

abstract：:Adenosine, dibutyryl cyclic AMP, monobutyryl cyclic AMP, cyclic AMP, and 5'-AMP have a remarkable morphogenetic effect on cultured iris epithelial cells obtained from adult newt. They alter the broad undulating membrane of the cell into branching strands of cytoplasm, a configuration that has been named "stellate." Th...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Ortiz JR,Yamada T,Hsie AW

更新日期：1973-08-01 00:00:00

abstract：:The suggested role of adenosine 3':5'-cyclic monophosphate as the "second messenger" in the neurite outgrowth from chick embryonic sensory ganglia mediated by nerve growth factor was examined. Although N(6),O(2)-dibutyryl adenosine 3':5'-cyclic monophosphate induces fiber outgrowth at concentrations of 1-5 mM, this re...

journal_title：Proceedings of the National Academy of Sciences of the United States of America

authors： Frazier WA,Ohlendorf CE,Boyd LF,Aloe L,Johnson EM,Ferrendelli JA,Bradshaw RA

更新日期：1973-08-01 00:00:00