bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simple Method for the Detection of Mutagens in Urine: Studies with the Carcinogen 2-Acetylaminofluorene
Authors: Durston William E. , Ames Bruce N.
Published: May 2006

We described previously a simple test on petri plates for detecting many carcinogens as mutagens using an especially sensitive set of bacterial strains to detect mutagens and a rat, or human, liver homogenate for carcinogen activation. We now extend the utility of the method for the detection of mutagenic metabolites in urine. The addition of commercial β-glucuronidase (EC 3.2.1.31) to the petri plates along with the urine, liver homogenate, and bacteria allows detection of metabolites that are excreted in urine as β-glucuronide conjugates. By this method mutagenic activity is readily demonstrated with urine of rats that were administered as little as 200 μg (1.6 mg/kg) of the carcinogen, 2-acetylaminofluorene. In this case the major urinary metabolite that we detect appears to be a glucuronide conjugate. We propose that the method be used for the screening of human urines in order to detect mutagenic metabolites of drugs and of dietary components. It may also be useful for testing of urinary metabolites of drugs and food additives in experimental animals.
Ethological Isolation Among Three Species of the
planitibia
Subgroup of Hawaiian
Drosophila
Authors: Ahearn J. N. , Carson H. L. , Dobzhansky Th. , Kaneshiro K. Y.
Published: May 2006

Drosophila heteroneura
and
D. silvestris
are sympatric species living on the island of Hawaii, while
D. planitibia
is allopatric on the nearby island of Maui. A pronounced ethological isolation is found between the sympatric species, and none between allopatric ones, except that
D. planitibia
females discriminate against
D. heteroneura
males. Male hybrids are sterile in allopatric crosses but fertile in sympatric ones. The ethological isolation and the hybrid sterility are uncorrelated. This is expected if premating isolation between closely related species is an
ad hoc
product of natural selection, while postmating isolation is an incidental result of genetic divergence. Some exceptions to the rule are discussed.
Identification of a High Affinity Nuclear Acceptor Site for Estrogen Receptor of Calf Uterus
Authors: Puca Giovanni Alfredo , Sica Vincenzo , Nola Ernesto
Published: May 2006

By means of affinity chromatography, specific nuclear acceptor sites for estradiol receptors are identified in a fraction that can be solubilized from purified nuclei with 2 M NaCl. Interaction between these acceptor sites and crude or partially purified estradiol receptor shows a high association constant (over 10
9
M). Receptor-acceptor interaction is dependent on physiological concentrations of 17β-estradiol; it is disrupted by high ionic strength. The nuclear acceptor sites appear to be protein in nature and exist in 5- to 10-fold excess over the estrogen binding sites present in the cytosol. Single- or double-stranded DNA does not bind estrogen-receptor complexes. Acceptor sites appear to be associated with basic nuclear proteins as judged by hydroxyapatite chromatography. The nuclear acceptor sites probably represent less than 0.1% of the purified basic proteins from the nucleus.
Activity of Colicin E3-Treated Ribosomes in Initiation and in Chain Elongation
Authors: Tai Phang-Cheng , Davis Bernard D.
Published: May 2006

Colicin E3 (called E3 here) is shown to act on polysomal ribosomes as well as on free ribosomes. This treatment severely inhibits subsequent chain elongation, both on preformed polysomes completing their nascent chains and on ribosomes translating poly(U). Elevated Mg
++
concentration relieves this inhibition. However, elevated Mg
++
concentration does not relieve the inhibition of ribosomes initiating on natural messenger; hence damage by E3 appears to have an additional, specific effect on some stage in initiation.

The effect of damage by E3 resembles that of streptomycin in several respects. This similarity suggests that the two agents may act on closely related sites on the ribosome.
Mechanism of Lysergic Acid Diethylamide Interference with Rabbit Antibody Biosynthesis
Authors: Voss Edward W. , Winkelhake Jeffrey L.
Published: May 2006

Lymphoid cells from hyperimmune rabbits producing antibodies to a hapten, incubated in the presence of
d
-lysergic acid diethylamide, continued to synthesize protein at a normal rate. Isoelectric focusing analysis of the low-molecular-weight protein secreted by the cells incubated with lysergic acid diethylamide indicated two components, with pI's of 4.9 and 5.2. Immune cells not exposed to lysergic acid diethylamide secreted only 7S IgG molecules with an average pI of approximately 7.0.
A Platelet-Dependent Serum Factor That Stimulates the Proliferation of Arterial Smooth Muscle Cells
In Vitro
Authors: Ross Russell , Glomset John , Kariya Beverly , Harker Laurence
Published: May 2006

Dialyzed serum from clotted monkey blood (“blood serum”) promotes the proliferation of monkey arterial smooth muscle cells in culture, but dialyzed serum prepared from recalcified platelet-poor plasma (“plasma serum”) is much less effective. Addition of platelets and calcium to platelet-poor plasma increases the activity of plasma serum to the same level achieved with blood serum. Furthermore, addition to plasma serum of a platelet-free supernatant prepared by exposing purified platelets to thrombin also stimulates the proliferation of smooth muscle cells. Thus, much of the growth-promoting activity of dialyzed serum is directly or indirectly derived from platelets. This finding has important implications for the response of arteries to localized injury and provides a key to further understanding of the role of factors derived from blood serum in promoting cell proliferation
in vitro
.
Antigen-Secreting Cells: Enumeration of Immunoglobulin-Allotype-Secreting Cells in Nonimmunized Rabbits by Means of Hybrid-Antibody-Coated Erythrocytes in a Reverse Hemolytic Plaque Assay
Authors: Molinaro Giuseppe A. , Maron Elchanan , Dray Sheldon
Published: May 2006

A reverse hemolytic plaque-forming cell (PFC) assay for the enumeration of immunoglobulin-(Ig)secreting cells in nonimmunized rabbits was developed by using erythrocytes coated with anti-Ig antibody. These indicator cells lysed after reacting with the secreted Ig antigen and complement. The anti-Ig antibodies used were specific for the b4 or b5 allotypic specificities, which are antigenic determinants on the kappa chain of rabbit Ig and controlled by alleles at the
b
locus. We coated erythrocytes with anti-b4 or anti-b5 antibody, using hybrid antibody with dual specificity to sheep red blood cells and to the b4 or b5 kappa chain. The coated erythrocytes were plated with cells from various lymphoid organs of nonimmunized rabbits. These lymphoid cells formed allotype-specific plaques, i.e., the cells of b4 homozygous rabbits formed hemolytic plaques with anti-b4 but not with anti-b5-coated erythrocytes and vice versa. In eight nonimmunized rabbits, 0.06-0.3% of the spleen cells (590-2900 PFC per 10
6
cells) secreted the
b
locus Ig allotypes. In three nonimmunized rabbits, 320-590 PFC per 10
6
cells were counted in the lymph node or bone marrow; 26-40 PFC per 10
6
cells were detected in the thymus. Since the b4 and b5 specificities are present on approximately 90% of the serum Ig, our results indicate that less than 1% of the lymphoid cells in nonimmunized rabbits secrete Ig at any one time. By this reverse PFC assay, Ig-secreting cells were for the first time detected as antigen-secreting cells. This assay can be applied to the detection of cells secreting other antigens.
The Effect of Pressure on the Molecular Complex of Isoalloxazine and Adenine
Authors: Weber Gregorio , Tanaka Fumio , Okamoto Byron Y. , Drickamer Harry G.
Published: May 2006

The effect of pressure to 10 kilobars on the fluorescence characteristics of flavin mononucleotide (FMN), flavin-adenine dinucleotide (FAD), and on complexes of FMN with adenylic acid (AMP), and with I
-
has been studied. The properties measured include peak location, fluorescence yield, and lifetime. From these results the equilibrium constant
K
and the rate constant
k
+
*
for complex formation were evaluated as a function of pressure. The pressure dependence of these coefficients shows that the volume of the system decreases upon complex formation and that there is an expansion upon formation of the activated complex (Δ
V
‡ is positive). The implications of these results for protein denaturation are mentioned.
Viral DNA·RNA Hybrids in Cells Infected with Simian Virus: The Simian Virus 40 Transcriptional Intermediates
Authors: Girard Marc , Marty Louise , Manteuil Simone
Published: May 2006

Brief labeling of cells infected with simian virus 40 with tritiated uridine resulted in the incorporation of part of the label into material that was soluble in 1 M NaCl and sensitive to KOH, with a buoyant density close to that of DNA. The properties of this material suggest that it represents single-stranded nascent molecules of messenger RNA of simian virus 40 hydrogen-bonded over a small portion of their length to viral DNA templates. The name “simian virus 40 transcriptional intermediate molecules” is suggested for these naturally occurring DNA·RNA hybrid molecules. The DNA in the hybrid seems to be in the form of replicative intermediate molecules.
Kinetic Evidence for the Presence of Two Postaglandin Receptor Sites Regulating the Activity of Intestinal Adenylate Cyclase Sensitive to
Escherichia coli
Enterotoxin
Authors: Kantor Harvey S. , Tao Pearl , Kiefer Helen Chilton
Published: May 2006

Kinetic behavior most consistent with the presence of two
independent
, but simultaneously acting, regulatory effector sites for prostaglandins has been presented for adenylate cyclase (EC 4.6.1.1) of rabbit intestinal epithelial cells. One site regulates activation of the catalytic site, while the other site regulates inhibition. A synthetic prostaglandin analogue, 7-oxa-13-prostynoic acid, is recognized at both sites in a concentration-dependent manner. At concentrations of 7-oxa-13-prostynoic acid less than 45 μg/ml, activation is seen, while at higher concentrations, inhibition is seen. Different naturally occurring prostaglandins appear to be site-specific. Prostaglandin E
1
gives only activation of the cyclase, while prostaglandin A
1
gives only inhibition of the activated cyclase. When saturating concentrations of prostaglandin E
1
are used to activate adenylate cyclase, no further activation by 7-oxa-13-prostynoic acid can be elicited, indicating that both molecules activate at the same site. The similarity of inhibition constants for both 7-oxa-13-prostynoic acid and prostaglandin A
1
suggests that the mode of binding is the same for both compounds and that they probably inhibit by acting at the same site. The inhibition by 7-oxa-13-prostynoic acid and by prostaglandin A
1
overrides enzyme activation produced by either
Escherichia coli
enterotoxin, prostaglandin E
1
, or sodium fluoride, suggesting that in intestinal adenylate cyclase this site is the primary regulatory site (i.e., primary allosteric effector site) for enzyme activity. These data suggest that sites exist on adenylate cyclase which would allow prostaglandins to serve as the intracellular messengers by which the cell controls its adenylate-cyclase-mediated response to extracellular stimulation, as with hormones.
Structure of an Iron(II) Dioxygen Complex; A Model for Oxygen Carrying Hemeproteins
Authors: Collman James P. , Gagne Robert R. , Reed Christopher A. , Robinson Ward T. , Rodley Gordon A.
Published: May 2006

The preliminary structural characterization of a reversible ferrous dioxygen complex is reported. Mono(
N
-methyl imidazole) (dioxygen)
meso
-tetra (α,α,α,α-
o
-pivalamidephenyl) porphinatorino(II), [Fe(O
2
)-(
N
-Me imid) (α,α,α,α-TpivPP)], 1, isolated from toluene solution, crystallizes in the monoclinic system with four molecules in a unit cell of dimensions
a
= 18.690 (3),
b
= 19.514 (3),
c
= 18.638 (3) Å, and β = 91.00 (1)°. R = 0.15 for 841 reflections having F
2
> 3σ (F
2
).

The complex 1 has four pivalamido groups on one side of the porphyrin forming a hydrophobic pocket of 5.4-Å depth which encloses coordinated dioxygen. The dioxygen is coordinated “end-on,” with a bent Fe-O-O bond. The Fe-O-O plane bisects an N-Fe-N right angle of the equatorial iron porphyrin plane and is four way statistically disordered. In addition there is a crystallographic 2-fold axis through iron, coordinated oxygen, and nitrogen of the axially bound
N
-methyl imidazole. Thus there are two types of coordinated dioxygen with the Fe-O-O plane either parallel or perpendicular to the trans axial imidazole plane. Corresponding values for the Fe-O-O bond angles are 135-(4)° and 137(4)° and for the O-O bond lengths are 1.23 (0.08) and 1.26 (0.08) Å, with a dihedral angle of 90° between alternative orientations of the Fe-O-O plane. The Fe-O distance is 1.75 (0.02) Å and Fe-N (imidazole) is 2.07 (0.02) Å, suggesting multiple bond character in the Fe-O moiety. The similarity of the Mössbauer spectrum of the model complex, 1, with oxyhemoglobin indicates that 1 may be a good model for oxygen binding in the oxygen transport hemeproteins.
An Intermediate Complex in the Dissociation of Aspartate Transcarbamylase
Authors: Evans David R. , Pastra-Landis Styliani C. , Lipscomb William N.
Published: May 2006

The multisubunit enzyme aspartate transcarbamylase consists of six copies of two types of polypeptide chains, catalytic (C) and regulatory (R). A complex formed by the partial dissociation of this enzyme has been isolated. This species, which has the structure C
6
R
4
, is a likely intermediate in the stepwise dissociation of aspartate transcarbamylase induced by mercurials. The formation of the complex is the result of the release of a single regulatory dimer (R
2
) from the parent molecule.

The specific activity of the intermediate is essentially the same as that of aspartate transcarbamylase. By contrast, both homotropic and heterotropic interactions are reduced, but not abolished. These observations suggest that the allosteric transitions involved in the control mechanisms do not require the intact structure C
6
R
6
.
Transfer RNA Conformation in Solution Investigated by Isotope Labeling
Authors: Gamble Ronald C. , Schimmel Paul R.
Published: May 2006

The incorporation of tritium into the C-8 position of purine residues in yeast tRNA
Phe
is shown to be markedly dependent on the conformation of the molecule. The completely unfolded molecule incorporates tritium at a rate commensurate to that expected for free purine nucleotides, but partially or completely folded forms incorporate proportionately less. The labeling of specific purine sites is determined by digesting the nucleic acid with a specific nuclease and analyzing each of the radioactive fragments produced. This analysis reveals that the amount of labeling of a purine in the folded form is strongly dependent upon its position in the sequence, whereas purine labeling in the unfolded form is independent of sequence position. The labeling pattern of the different bases in the folded form agrees fairly well with what is expected, based on existing solution and x-ray data on the conformation, i.e., residues involved in helical sections or apparently masked by tertiary interactions label more slowly than those on the “outside” of the molecule. Finally, folding and unfolding of specific regions of the macromolecule may be followed by the isotope labeling.
Replication of Colicin E1 Plasmid DNA in Cell Extracts: II. Selective Synthesis of Early Replicative Intermediates
Authors: Sakakibara Yoshimasa , Tomizawa Jun-Ichi
Published: May 2006

The major products of colicin E1 plasmid DNA synthesis in cell extracts are completely replicated molecules and a class of molecules containing newly synthesized small DNA fragments. The addition of 10% glycerol and/or 2 mM spermidine to extracts blocks synthesis of completely replicated molecules while enhancing synthesis of molecules containing newly synthesized DNA fragments. The latter molecules, which contain on the average two DNA fragments of approximately 6 S, are early replicative intermediates for synthesis of completely replicated molecules. Synthesis of the intermediates is sensitive to rifampicin and depends on RNA synthesis. RNA components are linked to the 6S DNA molecules.
The Three-State Model: A Minimal Allosteric Description of Homotropic and Heterotropic Effects in the Binding of Ligands to Hemoglobin
Authors: Minton Allen P. , Imai Kiyohiro
Published: May 2006

The effect of hydrogen ion, chloride, and 2,3-diphosphoglycerate upon the oxygen binding of hemoglobin may be satisfactorily described by an allosteric model employing three affinity states. The allosteric two-state model does not provide even an approximate description except under defined extreme conditions. In particular, the two-state model cannot provide a correct interpretation of recently reported electron spin resonance and nuclear magnetic resonance data.
Isolation and Function of the Gene
A
Initiator of Bacteriophage ϕX 174, A Highly Specific DNA Endonuclease
Authors: Henry Timothy J. , Knippers Rolf
Published: May 2006

The gene
A
product of
Escherichia coli
bacteriophage ϕX 174, necessary for initiation of ϕX DNA synthesis, has been identified and purified to near homogeneity. The gene
A
protein is shown to be a highly specific DNA endonuclease which breaks one phosphodiester bond in the viral strand of either double-stranded, circular ϕX replicative form I (RFI), or in single-stranded, circular ϕX viral DNA; it is inactive against all other species of DNA tested.
Requirement for a Functional Respiration-Coupled D-Fructose Transport System for Induction of Phosphoenolpyruvate: D-Fructose Phosphotransferase Activity
Authors: Wolfson Ellen B. , Krulwich Terry A.
Published: May 2006

Previous studies have shown that
Arthrobacter pyridinolis
can transport D-fructose or L-rhamnose using either a phosphoenolpyruvate:hexose phosphotransferase (phospho
enol
pyruvate:protein phosphotransferase, EC 2.7.3.9) system or a respiration-coupled transport system which requires the presence of exogenous L-malate. A mutant, AP4374, which is deficient in the D-fructose-specific component of the respiration-coupled system can grow on L-rhamnose using the phosphotransferase system, but cannot grow on D-fructose at all. AP4374 fails to produce the inducible D-fructose-specific phosphotransferase components (enzyme II and factor III) when grown in the presence of D-fructose. These results indicate a requirement for a functional respiration-coupled transport system for induction of the phosphotransferase system. The results further suggest that sufficient free D-fructose (or D-fructose 6-phosphate derived from it) must be present inside the cell in order for induction of the phosphotransferase system to occur. The entry of sufficient fructose to cause induction of the phosphotransferase system cannot occur by facilitated diffusion in the absence of energy coupling.
Distribution of Repetitive and Nonrepetitive Sequence Transcripts in HeLa mRNA
Authors: Klein William H. , Murphy William , Attardi Giuseppe , Britten Roy J. , Davidson Eric H.
Published: May 2006

Polyadenylated messenger RNA extracted from HeLa cells was hybridized with a mass excess of HeLa DNA. The kinetics of the hybridization reaction demonstrated that most of the messenger RNA is transcribed from nonrepetitive DNA. The amount of messenger RNA hybridized to DNA was measured both with and without prior RNase treatment. Comparison of the results indicates that within the limits of detection, HeLa messenger RNA does not contain repetitive sequence elements covalently linked to nonrepetitive sequence transcripts. However, a small fraction of the HeLa messenger RNA preparation is transcribed entirely from repetitive DNA sequences. This fraction represents about 6% of the total polyadenylated messenger RNA preparation.
Prolonged Transcription in a Cell-Free System Involving Nuclei and Cytoplasm
Authors: Wu Guang-Jer , Zubay Geoffrey
Published: May 2006

A cell-free system for nuclear-directed transcription has been developed that gives prolonged synthesis in the presence of cytoplasm. The nuclear and cytoplasmic components have been prepared from Krebs II ascites tumor cells for most experiments but further observations indicate that components prepared from other cell types may be used. After an initial 5- to 10-min period of relatively rapid RNA synthesis a linear rate ensues for 2-3 hr. In the absence of cytoplasm no net RNA synthesis occurs after the initial 10-min period. Experiments with α-amanitin suggest that about half of the cell-free synthesized RNA is made by RNA polymerase II, the enzyme believed to be responsible for messenger synthesis
in vivo.

The conditions used for RNA synthesis were derived from conditions found to be optimal for protein synthesis that proceeds linearly for 2-3 hr. It has not yet been possible to demonstrate the synthesis of protein from cell-free synthesized RNA in this system. A major problem here is that isolated nuclei, even when carefully washed, contain a great deal of translatable RNA.
Stimulation of Mitogenesis in Normal and Leukemic Human Lymphocytes by Divalent and Tetravalent Lima Bean Lectins
Authors: Ruddon Raymond W. , Weisenthal Larry M. , Lundeen Donna E. , Bessler Wolfgang , Goldstein Irwin J.
Published: May 2006

Two hemagglutinating components purified from the lima bean and composed of identical 62,000-molecular-weight subunits have mitogenic activity in normal and leukemic human lymphocyte cultures. Component II (247,000 molecular weight), a tetramer with four saccharide binding sites, is severalfold more active than component III (124,000 molecular weight), a dimer with two binding sites per molecule, as a mitogen for normal lymphocytes. Component II also stimulates mitogenesis in populations of cultured leukemic lymphocytes and appears to have greater activity than phytohemagglutinin-P in leukemic lymphocyte cultures obtained from some patients. Lima bean component III has minimal mitogenic activity toward leukemic lymphocytes. Components II and III appear to compete for the same cell-surface binding sites, but component II has a much greater capacity than component III to trigger DNA synthesis at low concentrations (2.5-25 μg/ml) in normal lymphocyte cultures. These results suggest that the mitogenic activity of lima bean lectin components is directly related to their valence.
Separation of Ribonuclease H and RNA Directed DNA Polymerase (Reverse Transcriptase) of Murine Type-C RNA Tumor Viruses
Authors: Wu Alan M. , Sarngadharan M. G. , Gallo Robert C.
Published: May 2006

Ribonuclease H (RNA·DNA-hybrid ribonucleotidohydrolase, EC 3.1.4.34) has been reported to copurify with reverse transcriptase (RNA directed DNA polymerase) of RNA tumor viruses. In addition, viral specific ribonuclease H and reverse transcriptase of avian type-C viruses are thought to be part of the same polypeptide. In this report we show that a fraction of the ribonuclease H activity from Rauscher murine leukemia and Kirsten murine sarcoma viruses was separated from reverse transcriptase by anion exchange chromatography while the remaining portion co-purified with the viral polymerase. The amount of this co-purified nuclease activity was about 4- to 8-fold lower than the activity found in avian myeloblastosis virus (with respect to the ratio of ribonuclease H to reverse transcriptase) and this nuclease activity can only be detected by using labeled substrate of high specific radioactivity. However, a complete separation of ribonuclease H activity from reverse transcriptase was obtained by purifying core structures of the virus by sucrose density gradient centrifugation. While reverse transcriptase was present in the cores, there was no detectable ribonuclease H. Furthermore, a specific antibody against Rauscher leukemia virus reverse transcriptase did not inhibit any virion associated ribonuclease H activity. Our results suggest that in these virions these two enzyme activities reside in two separate molecules and probably in two different compartments of the virus. These findings emphasize a basic difference between the avian and murine type-C virus DNA polymerases.
Characterization of a Protein Species Isolated from HeLa Cell Cytoplasm by Affinity Chromatography on Polyadenylate-Sepharose
Authors: Blanchard J. M. , Brissac C. , Jeanteur Ph.
Published: May 2006

Chromatography of different soluble extracts from HeLa cells on poly(A)-Sepharose columns has allowed the isolation of a protein fraction eluted by 0.2 M NaCl and localized predominantly in the cytoplasmic supernatant and in the 0.5 M KCl ribosomal wash. This fraction is present in large amounts (around 3% of total cytosolic proteins) and appears to contain a major protein species that is acidic on electrofocusing (pI around 4.5) and phosphorylated. It runs on glycerol gradients and Sephadex G-200 chromatography close to the aldolase marker (158,000 daltons) and dissociates into apparently identical subunits of 38,000 ± 2,000 daltons on sodium dodecyl sulfate-acrylamide gels, suggesting a tetrameric structure.
Generation of Specific Repeated Fragments of Eukaryote DNA
Authors: Mowbray S. L. , Landy A.
Published: May 2006

Calf-thymus DNA, hydrolyzed with a site-specific endonuclease from
Haemophilus influenzae
Rd, yields 12 discrete bands on polyacrylamide-agarose gels. These range in size from 7.5 × 10
4
to 2 × 10
6
daltons, and they represent about 5% of the total DNA with individual fragments comprising 0.1-1.5%. The various DNA segments are repeated between 1500 and 220,000 times per haploid genome. Whereas the wide range of reiteration frequencies suggests different origins for some of the fragments, the bias in fragment densities in CsCl and in Ag
+
-Cs
2
SO
4
toward those of known satellite DNAs suggests similar origins for some of them. Models for the possible origin of the DNA fragments can be grouped into three distinct, experimentally distinguishable, classes.
Proton Nuclear Magnetic Resonance Investigations and Ring Current Calculations of Guanine N-1 and Thymine N-3 Hydrogen-Bonded Protons in Double-Helical Deoxyribonucleotides in Aqueous Solution
Authors: Patel Dinshaw J. , Tonelli Alan E.
Published: May 2006

Methods are outlined for assigning the guanine-N
1
H and thymine-N
3
H protons to particular base pairs in the proton nuclear magnetic resonance spectra of double-stranded oligodeoxyribonucleotides of known sequence in aqueous solution. Ring current calculations have been used to evaluate the upfield shifts of the guanine-N
1
H and thymine-N
3
H protons from the pyrimidine and purine rings of nearest-neighbor base pairs in DNA B-type double-helical structures. Chemical shifts of 13.6 ± 0.1 ppm and 14.6 ± 0.2 ppm are assigned to the guanine-N
1
H proton of an isolated G·C base pair and the thymine-N
3
H proton of an isolated A·T base pair, respectively.
Denaturation: An Example of a Catastrophe
Authors: Kozak John J. , Benham Craig J.
Published: May 2006

We show that a “phase diagram” for the conformational states of proteins can be constructed using the mathematical theory of singularities of functions developed recently by René Thom. For proteins subjected to the disruptive influences of temperature and/or concentration of denaturing agent, this theory can be used as a predictive tool to account for the shape, sense, and changes in the curves that result when the optical rotatory dispersion is plotted as a function of these two constraints. The mathematical model is found to be in accord with known experimental data on collagen, lysozyme, and ribonuclease.
An RNA-Dependent Nucleoside Triphosphate Phosphohydrolase (ATPase) Associated with Rho Termination Factor
Authors: Lowery-Goldhammer Carolyn , Richardson John P.
Published: May 2006

Highly purified rho termination factor from
Escherichia coli
catalyzes an RNA-dependent hydrolysis of ribonucleoside triphosphates to nucleoside diphosphates and inorganic phosphate. In the presence of poly(C), a specific activity of 100 μmole of ATP hydrolyzed per min/mg has been measured. The phosphohydrolase activity appears to be associated with the protein responsible for termination of RNA synthesis, but a functional relationship between the two activities is not yet evident. Hydrolysis of nucleoside triphosphates occurs in the absence of termination and without any extensive degradation of RNA.
Particle Movements in Chloroplast Membranes: Quantitative Measurements of Membrane Fluidity by the Freeze-Fracture Technique
Authors: Ojakian George K. , Satir Peter
Published: May 2006

Stacked chloroplast membranes isolated from
Chlamydomonas reinhardtii
have differentiated particle arrays when examined by freeze-fracture electron microscopy. When the membranes are isolated unstacked, these particle arrays are lost and the fracture faces have a homogeneous appearance. The changes in appearance are due to rearrangement of existing membrane components by lateral particle movements in the plane of the fluid chloroplast membranes, since quantitative measurements demonstrate almost complete conservation of numbers and sizes of membrane particles during experimentally controlled stacking and unstacking.
Island Models for Takeover by a Social Trait Facing a Frequency-Dependent Selection Barrier in a Mendelian Population
Authors: Boorman Scott A.
Published: May 2006

A population genetic model is presented for selection of a Mendelian trait controlling for cooperative behavior between unrelated conspecifics. Under simple and robust assumptions, such a trait will be selected on a frequency-dependent basis, with a critical threshold frequency (β
2
crit
) of the social trait which must be exceeded before favorable selection of this trait can occur. Existence of this threshold gives rise to a basic evolutionary problem as to how evolution from an asocial state (β ≅ 0) to a social state (β ≅ 1) can take place. A formal model of this evolution is proposed which rests on obstacles to random mixing (population viscosity). The key fact is the possibility that an initial local concentration of the social trait may be able to spread out under the joint effects of selection and migration and eventually take over a much larger species population. It is argued that this model is the first formal model to capture the ideas of Wright concerning group selection of an altruist trait in an island-structured population.
Transcription of
Saccharomyces cerevisiae
Ribosomal DNA
In Vivo
and
In Vitro
Authors: Cramer Jane Harris , Sebastian Jesus , Rownd Robert H. , Halvorson Harlyn O.
Published: May 2006

In vivo
, ribosomal RNA of
Saccharomyces cerevisiae
is transcribed from the light strand of γ DNA.
In vitro
, γ DNA is transcribed with equal efficiency by both of the yeast nuclear RNA polymerases, polymerase I and polymerase II; however the RNA products synthesized by the two enzymes differ from each other both in size and in the relative composition of guanine and cytosine. RNA synthesized by polymerase I hybridizes preferentially to the light strand, while that synthesized by polymerase II hybridizes equally well to either strand. Selective transcription of the light strand of the ribosomal DNA also occurs when high-molecular-weight total nuclear DNA is used as template.
A Phosphate-Acceptor Protein Related to Parvalbumins in Dogfish Skeletal Muscle
Authors: Blum Hubert E. , Pocinwong Sitivad , Fischer Edmond H.
Published: May 2006

A phosphate-acceptor protein was isolated from the skeletal muscle of the Pacific dogfish (
Squalus acanthias
) displaying properties extremely similar to those of the parvalbumins, i.e., the low-molecular-weight, soluble, Ca-binding muscle proteins found in fish and amphibians. It has the same characteristic UV spectrum, strong affinity for calcium, and immunological crossreactivity with antibodies against homogeneous dogfish parvalbumin. Although it was isolated in three states of aggregation with molecular weights of about 350,000, 75,000, and 25,000, all species dissociate in Na dodecyl sulfate into subunits of 11,000 and 13,000 molecular weight. Furthermore, whereas no phosphorylation of parvalbumins could be demonstrated under any experimental conditions, the aggregated forms could be readily phosphorylated by a cyclic AMP-independent dogfish protein kinase, but not by phosphorylase kinase. One acid-stable and base-labile phosphate group was introduced per subunit which could be rapidly released by a dogfish protein phosphatase, but only very slowly if at all by phosphorylase phosphatase. It is speculated that this “phosphate-acceptor protein” might represent a physiologically active form of the parvalbumins.
Isolation of the Major Viral Glycoprotein and a Putative Precursor from Cells Transformed by Avian Sarcoma Viruses
Authors: Halpern Michael S. , Bolognesi Dani P. , Lewandowski Leon J.
Published: May 2006

Immune precipitation with a monospecific antiserum was employed to study the synthesis of the major viral glycoprotein gp85. Labeled gp85 was detectable by polyacrylamide gel electrophoresis of immune precipitates prepared from lysates of transformed cells which had been labeled for long term with radioactive amino acid or fucose. When immune precipitates were prepared from lysates of cells pulse-labeled with radioactive amino acid, the bulk of the precipitated counts did not appear in gp85 but in a heterogeneous protein fraction with a mean molecular weight of approximately 70,000; this fraction has been designated p70. If, however, the pulse label was followed by incubation of the cells in medium containing excess unlabeled amino acid, the bulk of the precipitated counts comigrated with gp85. Similar pulse-labeling experiments with radioactive fucose and glucosamine suggested that p70 represents incompletely glycosylated precursor to gp85.
An Antigen in Hodgkin's Disease Tissue Cultures: Radioiodine-Labeled Antibody Studies
Authors: Long John C. , Aisenberg Alan C. , Zamecnik Paul C.
Published: May 2006

An antiserum was prepared in rabbits against an antigen obtained by density gradient sedimentation of centrifuged medium from monolayer cultures of spleens involved by Hodgkin's disease. The antiserum was tested by isotopic antibody techniques with cells from each of eight cultures derived from spleens involved by Hodgkin's disease, four cultures derived from normal adult spleen, and one culture each of fetal spleen and thymus. By an indirect radioiodine-labeled antibody assay, anti-Hodgkin's disease globulin reacted with an antigen on the surface of cells from the Hodgkin's disease cultures, the quantity of which was related to the number of target cells and the amount of antibody used. This Hodgkin's disease tissue-culture antigen did not react with a rabbit antiserum against fractionated medium from a normal spleen culture, nor against
noncultured
Hodgkin's disease tumor tissue. The tumor specificity of the Hodgkin's disease tissue-culture antigen was assessed by a direct technique using
125
I-labeled anti-Hodgkin's disease globulin absorbed with either cultured Hodgkin's disease cells or with cultured normal cells. By this method the quantity of antigen on cells from Hodgkin's disease cultures was 15- to 30-fold greater than that on cells from normal cultures.

The Hodgkin's disease tissue-culture antigen is intimately associated with the propagation of the tumor in monolayer cultures, but its identity has not been established: it could be a viral component, a tumor or fetal antigen, or a normal tissue constituent.
Nuclear Ribonucleoprotein Complexes Containing Polyadenylate from Mouse Ascites Cells
Authors: Quinlan Thomas J. , Billings Peter B. , Martin Terence E.
Published: May 2006

Nuclear poly(A)-containing RNA of mouse ascites cells can be extracted in the form of 15-17S ribonucleoprotein complexes under conditions in which the bulk of the heterogeneous nuclear RNA is released as 30S complexes. The poly(A)-containing fraction of nuclear extracts has been resolved into two distinct components, 15 and 17 S; neither contains the two polypeptides of 30S ribonucleoprotein. The 17S particle contains approximately six polypeptide species of molecular masses 17,000-30,000 daltons. The 15S complex has four distinct polypeptides of higher molecular mass, including a prominent 80,000-dalton species.
The Evaluation of Configuration Coordinate Parameters from High Pressure Absorption and Luminescence Data
Authors: Okamoto B. Y. , Drotning W. D. , Drickamer H. G.
Published: May 2006

A configuration coordinate model was previously developed for relating the energies involved in optical and thermal electron excitations between two states and the effect of pressure on these energies. In the course of this development, expressions were presented for h
v
max
, the optical absorption peak maximum, and (
E
½
)

a

the peak half-width, as functions of pressure, and of the parameters defined in the model. The analysis was later extended to emission. We elaborate on the equations for the change of
hv
max
and
E
½
with pressure and discuss some of the problems involved in evaluating and using peak half-widths. Various combinations of absorption and emission data for evaluating the parameters describing the excitation are discussed and are compared for phenanthrene in various environments.
Nature of von Willebrand Factor: A New Assay and a Specific Inhibitor
Authors: Sarji Kay E. , Stratton Robert D. , Wagner Robert H. , Brinkhous K. M.
Published: May 2006

Platelet-active “von Willebrand factor” is a poorly characterized activity of a plasma-protein macromolecular complex. A new simple assay for von Willebrand factor is based on the dose response relation of the factor and the ristocetin platelet aggregation time. This assay uses the “snowstorm” macroscopic endpoint. A multiply transfused subject with von Willebrand's disease was observed to have a circulating inhibitor that blocks normal ristocetin aggregation of platelets, but not ADP-, epinephrine-, or collagen-induced aggregation. The inhibitor was not adsorbed by normal platelets, and was stable to heating at 56° for 30 min and to repeated freezings and thawings. This inhibitor also prevents action on human platelets by platelet-aggregating factor of bovine plasma, indicating this bovine factor activity is a function of von Willebrand factor. Three inhibitors were compared: (
1
) the von Willebrand factor inhibitor specifically blocked von Willebrand factor activity, (
2
) a human antibody from a hemophiliac inhibited only antihemophilic factor activity, and (
3
) a rabbit antiserum to a preparation of human antihemophilic factor inhibited both activities. The active site for von Willebrand factor on the macromolecular complex appears to be spaced some distance from the antihemophilic factor site.
Requirement of 3′-Terminal Poly(adenylic acid) for the Infectivity of Poliovirus RNA
Authors: Spector Deborah H. , Baltimore David
Published: May 2006

Ribonuclease H (EC 3.1.4.34) has been used to remove selectively much of the 3′-terminal poly(adenylic acid) [poly(A)] from poliovirus RNA by treating the RNA with the enzyme in the presence of poly(dT). Over 80% of the poly(A) could be removed and the residuum was found as oligo(A) stretches attached to many or all of the viral RNA molecules. Reduction of the size of the poly(A) markedly decreased the specific infectivity of poliovirus RNA, indicating that poly(A) is necessary to the infectivity of the RNA. The virions in plaques deriving from infection with treated RNA have a normal amount and size of poly(A), indicating that mechanisms exist in infected cells to regenerate normal length poly(A) from truncated poly(A).
Association Between Fighting Behavior and Catecholamine Biosynthetic Enzyme Activity in Two Inbred Mouse Sublines
Authors: Ciaranello Roland D. , Lipsky Ann , Axelrod Julius
Published: May 2006

Levels of three adrenal catecholamine synthesizing enzymes and isolation-induced fighting behavior were studied in two related sublines of the Balb/c inbred mouse strain. Enzyme levels were twice as high in the adrenals of Balb/cJ mice as in those of the Balb/cN mice; heterozygous progeny were intermediate between their parents in the levels of the three enzymes.

These sublines also showed marked differences in their fighting behavior after a 2-week isolation period. Balb/cJ mice fought immediately after presentation of an intruder mouse, while Balb/cN mice did not fight at any time during the test. Heterozygous progeny behaved more like the Balb/cN (non-fighters). Analysis of F
2
mice suggested that the differences in fighting behavior were determined by a single gene, with fighting being recessive.
The Importance of Gene Rearrangement in Evolution: Evidence from Studies on Rates of Chromosomal, Protein, and Anatomical Evolution
Authors: Wilson Allan C. , Sarich Vincent M. , Maxson Linda R.
Published: May 2006

We have compared the relative rates of protein evolution and chromosomal evolution in frogs and mammals. The average rate of change in chromosome number has been about 20 times faster in mammals than in frogs. Whereas it takes only 3.5 million years, on the average, for a pair of mammal species to develop a difference in chromosome number, the corresponding period for frogs is 70 million years. In contrast, the rate of protein evolution in mammals has been roughly equal to that in frogs. The rapid rate of gene rearrangement in mammals parallels both their rapid anatomical evolution and their rapid evolutionary loss of the potential for interspecific hybridization. Thus, gene rearrangements may be more important than point mutations as sources for evolutionary changes in anatomy and way of life.
Interaction of the Operator of the Tryptophan Operon with Repressor
Authors: Rose John K. , Yanofsky Charles
Published: May 2006

Transcription studies
in vitro
on repression of the tryptophan operon of
Escherichia coli
show that partially purified
trp
repressor binds specifically to DNA containing the
trp
operator with a repressor-operator dissociation constant of about 0.2 nM in 0.12 M salt at 37°, a value consistent with the extent of
trp
operon regulation
in vivo
. The half-life of the
trp
repressor-
trp
operator complex is less than 2 min
in vitro
in 0.12 M salt.
Sequence of Events in Initiation of Translation: A Role for Initiator Transfer RNA in the Recognition of Messenger RNA
Authors: Jay Gilbert , Kaempfer Raymond
Published: May 2006

It is shown that initiation of translation involves several steps. (
i
) Binding of fMet-tRNA
fMet
to the bacterial 30S ribosomal subunit in the absence of messenger RNA, yielding a 34S complex. This binding is rapid and dependent on initiation factor 2 but not on initiation factor 3. (
ii
) Binding of messenger RNA to the 34S complex. This binding is slower and depends on initiation factor 3. If R17 RNA is used as messenger, the resulting complex sediments at 46 S. (
iii
) Joining of a 50S subunit to yield a complete initiation complex. Binding of fMet-tRNA
fMet
not only precedes, but is necessary for, correct binding of messenger RNA to ribosomes. Thus, initiator tRNA may play an active role in the selection of initiation sites in messenger RNA.
Assignment of the Hydrogen Bonded Proton Resonances in (
Escherichia coli
) tRNA
Glu
by Sequential Melting
Authors: Hilbers C. W. , Shulman R. G.
Published: May 2006

The 300 MHz nuclear magnetic resonance peaks from the hydrogen bonded protons in (
Escherichia coli
) tRNA
Glu
in Mg
++
solutions have been measured at temperatures between 25° and 74°. Between 25° and 49° four resonances broaden, three of which are assigned to the hU arm and one to a G·C pair of the tertiary structure. By 64° these four resonances have disappeared and the nuclear magnetic resonance spectrum is fitted very well by a computer simulation based upon resonances from the acceptor, T-Ψ-C, and anticodon arms. At 66° the resonances from the T-Ψ-C arm are lost and at 74° only those from the anticodon are left. All 20 resonances expected from the cloverleaf model have been assigned by comparing the calculated positions of resonances in a particular arm with the stepwise loss of intensity with temperature. The root mean square error between calculated and observed positions is 0.17 ppm. Resonances at the end of helical regions which are sensitive to stacking beyond the helix allow us to conclude that the acceptor arm is stacked upon the T-Ψ-C in a regular helix and that G [unk]73 is stacked upon base pair [unk]1-72 but the hU and anticodon arms are not stacked in a regular helix upon the intervening base A [unk]27.
Gibberellic Acid Causes Increased Synthesis of RNA Which Contains Poly(A) in Barley Aleurone Tissue
Authors: Jacobsen John V. , Zwar John A.
Published: May 2006

Incubation of isolated barley aleurone layers with gibberellic acid for 16 hr caused a 50% increase in the synthesis of RNA that contains poly(A) sequences [poly(A)-RNA], but had no measurable effect on the syntheses of the major RNA species. The syntheses of both the poly(A) and the heteropolymeric fractions of the poly(A)-RNA were increased.

The poly(A) sequences were separated into two classes by size, one containing an average of 250 nucleotides and the other about 70 nucleotides. The two classes occurred in a molar ratio of about 1:1. Gibberellic acid increased the syntheses of both sequences to the same extent.

We interpret these results to mean that gibberellic acid increases specifically the synthesis of mRNA in this tissue.
Backbone Conformations in Secondary and Tertiary Structural Units of Nucleic Acids. Constraint in the Phosphodiester Conformation
Authors: Yathindra N. , Sundaralingam M.
Published: May 2006

The possible backbone phosphodiester conformations in a dinucleoside monophosphate and a dinucleoside triphosphate have been investigated by semiempirical energy calculations. Conformational energies have been computed as a function of the rotations ω′ and ω about the internucleotide P-O(3′) and P-O(5′) linkages, with the nucleotide residues themselves assumed to be in one of the preferred [C(3′)-
endo
] conformations. The terminal phosphates in a dinucleoside triphosphate greatly limit the possible conformations for the backbone (in a polynucleotide) compared to a dinucleoside monophosphate. There appear to be two major types of conformations that are favored for the backbone. The phosphodiester conformation (ω′,ω) ≃ (290°,290°) characteristic of helical structures is one of them, indicating that the polynucleotide backbone shows an inherent tendency for the helical conformation. The other favored conformation is centered at (ω′,ω) ≃ (190°,300°) and results in an extended backbone structure with unstacked bases. A third possible conformation centered at (ω′, ω) ≃ (200°, 60°) and the (190°, 300°) conformation appear to be important for the folding of a polynucleotide chain. The conformation (ω′,ω) ≃ (80°,80°), observed in a dinucleoside monophosphate and believed to be a candidate for producing an abrupt turn in a polynucleotide chain, is found to be stereochemically unfavorable in a dinucleoside triphosphate and a polynucleotide.