bluuebunny/crossref_metadata_2025 huggingface dataset:
Purification and Some Characteristics of 5S DNA from
Xenopus laevis
Authors: Brown Donald D. , Wensink Pieter C. , Jordan Eddie
Published: May 2006

DNA containing the multiple genes for 5S RNA has been isolated from the genome of
Xenopus laevis
. Whereas 5S RNA is about 57% G + C, the 5S DNA has a base composition of about 33-35% GC and consists of two alternating regions that differ in base composition by at least 20% GC. A denaturation map of 5S DNA analyzed by electron microscopy demonstrates that the repeating pattern is regular and each repeating unit has a mass of about 500,000 daltons. If one gene for 5S RNA (84,000 daltons native) were present in each repeat, it should comprise about 16.8% of 5S DNA. This arrangement is confirmed, since 6.8% of pure 5S DNA (13.6% of its base pairs) hybridized with 5S RNA. The remaining 83% of each repeating unit is considered to be “spacer” DNA. The 5S RNA hybridizes with about 0.05% of the bulk DNA of
X. laevis
, so that 5S DNA comprises about 0.7% of the total nuclear DNA. This is equivalent to about 24,000 repeating units for each haploid complement of DNA. These repeats are highly clustered; as many as 86 have been visualized along a single DNA molecule.
Cyanophycin Granules from the Blue-Green Alga
Anabaena cylindrica:
A Reserve Material Consisting of Copolymers of Aspartic Acid and Arginine
Authors: Simon Robert D.
Published: May 2006

The cyanophycin granules from two-week-old cultures of the blue-green alga
Anabaena cylindrica
were isolated by sonication of the cells followed by differential centrifugation. These particles are composed of polypeptides containing only two amino acids, aspartic acid and arginine, and have a molecular weight between about 25,000 and 100,000.
Calcium as a Regulator of the Proliferation of Normal, but Not of Transformed, Chicken Fibroblasts in a Plasma-Containing Medium
Authors: Balk Samuel D.
Published: May 2006

In a culture medium of low calcium concentration containing 5% heat-inactivated chicken plasma, normal chicken fibroblasts divide very slowly, while their counterparts transformed with Schmidt-Ruppin Rous sarcoma virus divide much more rapidly. In the same low-calcium medium, the use of heat-inactivated serum, rather than heat-inactivated plasma, results in rapid division of both normal and transformed cells.

The use of heat-inactivated plasma rather than serum, and the use of a low-calcium medium, combine to permit the demonstration of a marked difference between the proliferative behaviors of normal and neoplastic cells and suggest a basis for the autonomy of the latter.
Interactions between ADP and the Coupling Factor of Photophosphorylation
Authors: Roy Harry , Moudrianakis Evangelos N.
Published: May 2006

The coupling factor of photophosphorylation, which carries out the terminal steps in the light-dependent synthesis of ATP in spinach chloroplasts, forms tight complexes with [
14
C]ADP
in vitro
. The bound [
14
C]ADP undergoes a transphosphorylation reaction to give [
14
C]AMP and [
14
C]ATP. The [
14
C]ATP remains tightly bound, and can be recovered conveniently only by denaturation of the enzyme nucleotide complex. If spinach membranes are illuminated in the presence of pyocyanine and [
3
H]AMP or [
32
P]P
i
, the enzyme can be recovered as a tight complex with [
3
H]ADP or [
32
P]ADP. The evidence indicates that AMP is an earlier acceptor of phosphate than is ADP, in a light-driven phosphorylation reaction. It also suggests that AMP serves as a cofactor in photophosphorylation.
Light-Induced Electron-transfer Reactions between Chlorophyll
a
and Hydrogenated Pteridine Derivatives in Solution
Authors: Bobst A. M.
Published: May 2006

Preliminary studies of the formation of cationic 2 - amino - 6, 7 - dimethyl - 4 - hydroxy - 5, 6, 7, 8 - tetrahydropteridine radicals in alcoholic solution are reported. The results indicate that the same type of radical is formed either by oxidizing agents like hydrogen peroxide and iodine, or in a photoinduced reaction with chlorophyll
a
. A similarity between the epr signal of the light-induced cationic pteridine radical and the photoinduced epr signal II in photosynthesis is observed.
Hour-Glass Behavior of the Circadian Clock Controlling Eclosion of the Silkmoth
Antheraea pernyi
Authors: Truman James W.
Published: May 2006

The emergence of the Pernyi silkmoth from the pupal exuviae is dictated by a brain-centered, photosensitive clock. In continuous darkness the clock displays a persistent free-running rhythm. In photoperiod regimens the interaction of the clock with the daily lightdark cycle produces a characteristic time of eclosion. But, in the majority of regimens (from 23L:1D to 4L:20D), the eclosion clock undergoes a discontinuous “hourglass” behavior. Thus, during each daily cycle, the onset of darkness initiates a free-running cycle of the clock. The next “lights-on” interrupts this cycle and the clock comes to a stop late in the photophase. The moment when the Pernyi clock stops signals the release of an eclosion-stimulating hormone and is demonstrated to be a function of the time when the free-running cycle is interrupted by lights-on. Moreover, the width (duration) of the eclosion peak in a photoperiod is shown to be dependent upon the length of the dark phase, and, consequently, upon the amount of the free-running cycle that is completed. This relationship demonstrates that the free-running cycle may be divided into two parts. The attainment of maximal accuracy (and thus the narrowest eclosion peak) is dependent upon the completion of only the first 2 hr of the free-running cycle. The completion of succeeding portions of the cycle, while having an effect upon the time of eclosion, no longer affects the accuracy of the clock. A mechanistic model of the eclosion clock is presented.
Compounds I of Catalase and Horse Radish Peroxidase: π-Cation Radicals
Authors: Dolphin D. , Forman A. , Borg D. C. , Fajer J. , Felton R. H.
Published: May 2006

Two-electron oxidation of cobaltous octaethylporphyrin [Co(II)(Et)
8
P] yields a stable π-cation radical [Co(III)(Et)
8
P]
2+.
, the optical spectrum of which exhibits spectral changes dependent upon the nature of the counterion. Comparison of these spectra with those of Compounds I of horseradish peroxidase and catalase leads us to propose that these Compounds I contain a π-cation radical of the heme prosthetic group. This proposal explains the oxidation level, optical spectra, and stability of the primary compounds without recourse to properties such as stoichiometric mixtures of special porphyrins, stable Fe(V) porphyrins, or unique conformers of heme porphyrins. Explanations are advanced to account for the missing electron spin resonance signal of Compound I of horseradish peroxidase.
One- and Two-Fluid van der Waals Theories of Liquid Mixtures, II. 6:12 Molecules
Authors: Henderson Douglas , Leonard Peter J.
Published: May 2006

The equation of state of mixture of 6:12 molecules is calculated using the one- and two-fluid van der Waals theories, the three-fluid theory, and the Flory theory. The one-fluid van der Waals theory is found to be in the best agreement with the quasi-experimental, machine-simulation results.
The Carboxyl Transferase Component of Acetyl CoA Carboxylase: Structural Evidence for Intersubunit Translocation of the Biotin Prosthetic Group
Authors: Guchhait Ras B. , Moss Joel , Sokolski Walter , Lane M. Daniel
Published: May 2006

An essential protein component of acetyl CoA carboxylase, isolated and extensively purified from cell-free extracts of
Escherichia coli
, has been identified as malonyl CoA:
d
-biotin carboxyl transferase. This enzyme, which does not contain covalently-bound biotin, catalyzes carboxyl transfer from malonyl CoA to free
d
-biotin, a model reaction for the second step in the carboxylation of acetyl CoA. The transcarboxylation product, after stabilization by methylation, was identified as 1′-
N
-carboxy-
d
-biotin dimethyl ester. These results indicate the presence of a biotin site on the carboxyl transferase, distinct from that on the biotin carboxylase, which carries out the first step in the overall process. In addition, the carboxyl transferase catalyzes a slower abortive decarboxylation of malonyl CoA, thus indicating that carboxyl abstraction and protonation do not require the participation of biotin.

It is now evident that the half-reactions of acetyl CoA carboxylation are catalyzed by biotin carboxylase and carboxyl transferase. Both components are devoid of biotin and have specific binding sites for free
d
-biotin, as well as for their respective substrates; hence, the acetyl CoA carboxylation mechanism must involve intersubunit translocation of the carboxylated biotinyl group, which is bound covalently to carboxyl-carrier-protein, a noncatalytic polypeptide.
On the Concept of Orbital Steering in Catalytic Reactions
Authors: Bruice Thomas C. , Brown Allister , Harris David O.
Published: May 2006

Angular displacement from linear overlap of but a few degrees in the transition state of the enzyme-substrate complex has been postulated to be of great kinetic significance (“orbital steering”). The concept of orbital steering is shown to have evolved from the orientation parameters of an equation previously proposed to evaluate the kinetic importance of propinquity. This equation is shown to be naive. Arguments provided against the concept of orbital steering include: (
a
) force constants predicted from orbital steering are about 100 times those experimentally determined from displacement of nuclei in a direction normal to the axis of a covalent bond (for example, at room temperature vibrational bending amplitudes of +5° or more are common); (
b
) because of the lessened directionality of orbitals containing nonbonded electron pairs, the force constants in transition states should be even smaller than in the case of a covalent bond; and (
c
) molecular orbital calculations predict shallow total energy minima for orbital alignment. The experimental rate data offered as a basis for the concept of orbital steering are shown to find rationalization in the previously observed dependence of ΔS‡ on kinetic order and the energy requirements for the freezing-out of single bonds in the transition state leading to the formation of medium-size ring compounds from extended ground states. It is concluded that if orbital steering does exist, experimental and theoretical evidence to support this concept have yet to be presented.
Induction of Mitochondrial DNA Synthesis in Monkey Cells Infected by Simian Virus 40 and (or) Treated with Calf Serum
Authors: Levine Arnold J.
Published: May 2006

Infection of confluent monolayer cultures of African green monkey kidney cells with simian virus 40 results in an enhanced synthesis of nuclear and mitochondrial DNA. This is demonstrated both by an increased rate of incorporation of [
3
H]thymidine into mitochondrial DNA and by detection of increased amounts of mitochondrial DNA in infected cells. With monkey BSC-1 cells, where SV40 infection does not result in a stimulation of nuclear DNA synthesis, no stimulation of mitochondrial DNA synthesis is observed. SV40 infection of mouse 3T3 cells also stimulates nuclear and mitochondrial DNA synthesis.
Karyotyping of Single Human Chromosomes from Dry Mass Determined by Electron Microscopy
Authors: Bahr Gunter F. , Golomb Harvey M.
Published: May 2006

Human chromosomes from cultures of peripheral lymphocytes were prepared for electron microscopy by surface spreading and critical-point drying. Total and partial determinations of chromosomal dry mass were made from contrast in electron microscopic negatives. The distribution of dry weights was analyzed with respect to the Denver-Chicago classifications. There is considerable variability of mass within each group, but no statistically significant differences between four donors. A single chromosome can be correctly classified from its total mass and the ratio of long- to short-arm mass.
Demonstration of Imino Acids as Products of the Reactions Catalyzed by D- and L-Amino Acid Oxidases
Authors: Hafner Edmund W. , Wellner Daniel
Published: May 2006

It had long been thought, but never demonstrated, that imino acids are formed in the reactions catalyzed by D- and L-amino acid oxidases (EC 1.4.3.3 and 1.4.3.2). The formation of imino acids is now shown directly by allowing the amino acid oxidase reaction to proceed in the presence of NaBH
4
, when the imino acid is reduced to the corresponding racemic amino acid. Thus, when NaBH
4
is added to a mixture of D-amino acid oxidase and D-alanine, a significant amount of L-alanine is formed. Analogous results are obtained using L-amino acid oxidase and L-leucine. Since D-amino acid oxidase is active in the presence of NaBH
4
, L-alanine continues to be formed until most of the D-isomer is oxidized by the enzyme. This reaction provides a new method for inverting the configuration of an amino acid.

When NaBH
4
is added to a system containing D-amino acid oxidase plus D-alanine and L-lysine, free ε-
N
-(1-carboxyethyl)-L-lysine is formed. When bovine serum albumin is substituted for L-lysine, the same compound results upon acid hydrolysis. It is concluded that the amino acid oxidase reaction produces a free imino acid, which may be reduced by NaBH
4
to a racemic amino acid or may form Schiff's bases by reaction with the ε-amino groups of proteins and of free lysine.
In Vitro
Transformation of Rodent Cells by K-Region Derivatives of Polycyclic Hydrocarbons
Authors: Grover Philip L. , Sims Peter , Huberman Eliezer , Marquardt Hans , Kuroki Toshio , Heidelberger Charles
Published: May 2006

The K-region epoxides and
cis
-dihydrodiols derived from benz(a)anthracene and from dibenz(a,h)-anthracene have been found to be more active in the production of malignant transformation in hamster embryo cells than the hydrocarbons or the corresponding K-region phenols. The K-region epoxides derived from benz(a)-anthracene and from 3-methylcholanthrene were also active in transforming a clone of ventral prostate cells from the C3H mouse that was not readily transformed by the parent hydrocarbons. The phenols were the most toxic compounds tested but did not transform cells; this confirms that toxicity and transformation are not directly related events. The results obtained support the view that metabolism of polycyclic hydrocarbons precedes toxicity and transformation in rodent cells in culture.
Evidence for the Existence of Several Molecular Species in the “45S Fraction” of Mammalian Ribosomal Precursor RNA
Authors: Tiollais Pierre , Galibert Francis , Boiron Michel
Published: May 2006

Analysis of RNA (after 5 or 60 min of labeling with [
3
H]uridine) from L5178Y cells by electrophoresis in 1.7% polyacrylamide gels demonstrates that the ribosomal RNA “45S fraction“ is not homogeneous but consists of at least three molecular species, conventionally designated 47S RNA, 46S RNA, and 45S RNA. Alternatives to the classical scheme for the biosynthesis of ribosomal RNA in mammalian cells are discussed.
Heavy-Chain Variable Regions in Normal and Pathological Immunoglobulins
Authors: Wang A. C. , Fudenberg H. H. , Pink J. R. L.
Published: May 2006

Aminoacid sequence analysis of immunoglobulin G heavy chains from each of 15 normal individuals showed the presence of VHIII subgroup sequences in all individuals, to an extent of about 15-25% of the total. Therefore, different subgroups of the heavy-chain variable region are not products of alleles of a single gene.

N-terminal aminoacid sequences were determined for ten heavy chains of myeloma proteins that belonged to the VHIII subgroup. Our results demonstrate the existence of a “hypervariable“ region of sequence between positions 30 and 35, homologous to one of the three hypervariable regions of light chains. At several positions, variants of the basic sequence are repeated in different proteins. It is likely that such variants are derived from several recently evolved genes that constitute the VHIII subgroup.
DNA Synthesis in Mixed Cultures of Rat Leukocytes and Allogeneic Dissociated Skin Cells
Authors: Main Raymond K. , Cochrum Kent C. , Jones Marjorie J. , Kountz Samuel L.
Published: May 2006

A proliferative response (increased DNA synthesis measured by [
3
H]thymidine incorporation; maximum at the fifth day) occurs in mixed cultures of rat peripheral leukocytes and allogeneic dissociated skin cells. This response is allospecific and is greater than that occurring in mixed cultures of corresponding allogeneic leukocytes. This mitogenic property of dissociated skin cells is not shared with other nonlymphoid cell types, for example kidney cells. Cells from four isogenic rat strains have been studied; proliferative responses occurred in the mixed cell cultures only when cell donors differed by alleles at the Ag-B histocompatibility locus.
Interaction of Aromatic Amino Acids with Neutral Polyadenylic Acid
Authors: Raszka M. , Mandel M.
Published: May 2006

The aromatic amino acids tryptophan, phenylalanine, and histidine interact with singlestranded polyadenylic acid [poly(A)] as observed by proton magnetic resonance spectroscopy. The chemical shift of the C
2
and C
8
protons of the adenine moiety of poly(A) is consistent with a destacking of the initially partly-stacked polynucleotide chain by the intercalation of the planar ring structure. The relative magnitude of this interaction is tryptophan>phenylalanine>histidine.
Acetoxycycloheximide and Transient Amnesia in the Rat
Authors: Serota Roger G.
Published: May 2006

Rats were trained during the severe inhibition of protein synthesis that follows intracerebral injection of acetoxycycloheximide. Amnesia was consistently observed 24 hours after training, but memory spontaneously returned within 6 days. There was, consequently, no evidence of interference by acetoxycycloheximide with the consolidation phase of memory, but rather a transient deficit in the retrieval phase. It is suggested that this deficit may be due to a deficiency in neurotransmitters.
Insulin-Receptor Interactions in Adipose Tissue Cells: Direct Measurement and Properties
Authors: Cuatrecasas Pedro
Published: May 2006

An assay system is described for measurement of specific binding of [
125
I]insulin to intact fat cells and membrane fractions from such cells. The binding is time- and temperature-dependent and saturable with respect to insulin; the bound insulin is displaced by native insulin but not by oxidized or reduced insulin or by a number of other peptide hormones. A maximum of about 11,000 molecules of insulin can bind per cell. The insulin-receptor association is a bimolecular reaction with a rate constant of 1.5 × 10
7
M
-1
sec
-1
, while the dissociation is a strictly first-order process with a rate constant of 7.4 × 10
-4
sec
-1
. A dissociation constant of 5.0 × 10
-11
M can be calculated from these rate constants, whereas a value of 6.1 × 10
-11
M is obtained on the basis of enhancement of glucose oxidation. Complex formation does not result in chemical change or inactivation of insulin or receptor. The total binding capacity of fat cells is quantitatively recovered in the particulate fraction after homogenization. The insulin-cell receptor interaction is a simple dissociable process involving a homogeneous species probably present exclusively in the cell membrane.
Organelle Mutations and Their Expression in
Chlamydomonas reinhardi
Authors: Surzycki Stefan J. , Gillham Nicholas W.
Published: May 2006

A new method for classifying Mendelian and non-Mendelian antibiotic-resistant mutants in
Chlamydomonas reinhardi
is proposed. This classification takes into account the cellular site of expression of the resistant phenotype, the location of genetic information for resistance in the cell, and the pattern of inheritance of the different mutants. The classification is consistent with the idea that
C. reinhardi
contains three protein-synthesizing systems, two of which are sensitive to antibacterial antibiotics and located in the chloroplast and mitochondria, respectively. The information for resistance can be coded either in the chloroplast, the mitochondria, or the nucleus. A new experimental approach to the problem of cellular localization of mutations to antibiotic resistance is prescribed and used for the classification of known resistant mutations.
Temperature-Sensitive Mutations in
Drosophila melanogaster
, VIII. The Homeotic Mutant,

ss
a40a
Authors: Grigliatti Thomas , Suzuki David T.
Published: May 2006

There exists in
Drosophila
a class of mutations called “homeotic” that cause changes in determination of the imaginal discs. The homeotic mutant,

ss
a40a

, was found to have a temperature-sensitive transformation of the arista segment of the antennal complex to a tarsus of the leg. In a selected stock penetrance was complete, so that at 29°C normal aristae were produced, whereas at 17°C complete tarsi developed in all flies. “Temperature-shift” studies revealed a temperature-sensitive period in the third larval instar. The temperature-initiated action of

ss
a40a

does not appear to result from a simple wave or gradient of determination passing through the disc. Shifts up during the temperature-sensitive period yielded leg tissue proximally, which increased distally with progressively later shifts. Shifts down yielded leg tissue at the aristal base, which retreated with later shifts.
Relation of the Conformation of Oxytocin to the Biology of Neurohypophyseal Hormones
Authors: Walter Roderich , Schwartz I. L. , Darnell J. H. , Urry D. W.
Published: May 2006

The conformation of oxytocin is related to the evolution and to some of the biological activities of neurophypophyseal hormonal peptides. On the basis of the three-dimensional structure, positions 3, 4, 7, and 8 are the only loci at which naturally occurring neurohypophyseal peptides may be expected to differ. The side chains of these amino-acid residues are the primary determinants of the differential specificity in interactions between neurohypophyseal hormones and their receptors.

There are three general groups of structural modifications of neurohypophyseal hormones which can be correlated with specific changes in biological activity: (
a
) those affecting the stabilization of the backbone of the peptide, which would extensively perturb the spatial relationships among all the constituent amino acids and hence, affect both affinity and intrinsic activities uniformly; (
b
) those which, while retaining the stability of the backbone conformation, alter the steric environment and charge distribution of limited surface areas, and thereby can affect affinity and intrinsic activity differentially; and (
c
) those changing the steric and electronic requirements of moieties comprising the active surface of the neurohypophyseal peptide, without perturbing the peptide backbone of the hormone molecule and, hence, affecting intrinsic activity without altering affinity.
Acetyl CoA Carboxylase: Isolation and Characterization of Native Biotin Carboxyl Carrier Protein
Authors: Fall R. Ray , Nervi A. M. , Alberts Alfred W. , Vagelos P. Roy
Published: May 2006

A large form of biotin carboxyl carrier protein (BCCP
L
) has been isolated from extracts of
Escherichia coli
. It has a minimal molecular weight of 20,000, according to its behavior on sodium dodecylsulfate-polyacrylamide gel electrophoresis, and contains approximately 1 mol of biotin per 22,000 g of protein. BCCP
L
exhibits
K
m
values, in the biotin carboxylase and transcarboxylase half-reactions of acetyl CoA carboxylase, of 2 × 10
-7
M and 4 × 10
-7
M, respectively; these values are 50-100 times lower than those obtained with smaller forms of BCCP previously isolated. Electrophoresis of crude extracts of
E. coli
indicates that the major biotin-containing protein migrates at the same rate as BCCP
L
, which suggests that BCCP
L
is the native form of BCCP in
E. coli
.
Effect of Gravity on Osmotic Equilibria
Authors: Scholander P. F. , Perez M.
Published: May 2006

Experiments with colloidal suspensions of oil and iron oxide at equilibrium show that the buoyancy of the suspended particles is additive to the osmotic pressure and that the relation remains with the free surface and not with the membrane. The experiments contribute to the general concept that osmotic pressure is caused by the dispersal pressure of solute molecules and that the osmotic interaction with the water at equilibrium is due solely to a coupling at the free surface.
The First Steps of Magnification of DNA Complementary to Ribosomal RNA in
Drosophila melanogaster
Authors: Ritossa F. , Malva C. , Boncinelli E. , Graziani F. , Polito L.
Published: May 2006

Those
Drosophila bobbed
males whose progeny exhibit the phenomenon of “rDNA magnification” are shown to have higher rates of rRNA synthesis than normal males. Further evidence that the magnification process is characterized by a stepwise accumulation of rDNA was obtained. A working hypothesis to explain the magnification process is advanced.
A Carotenogenic Enzyme Aggregate in
Phycomyces:
Evidence from Quantitive Complementation
Authors: Guardia M. D. De La , Aragón C. M. G. , Murillo F. J. , Cerdá-Olmedo E.
Published: May 2006

Wild-type
Phycomyces blakesleeanus
accumulates β-carotene, while the mutant strain C2 is unable to synthesize carotenoids, and the mutant strain C9 accumulates lycopene. Heterokaryons containing a proportion,
p
, of C2 nuclei and (l —
p
) of C9 nuclei accumulate lycopene, γ-carotene, and β-carotene in the relative amounts (l —
p
),
p
(l —
p
), and
p
2
, respectively, for different values of
p
.

It is shown that these results are expected from the operation of a carotenogenic enzyme aggregate that works as an assembly line and contains two copies of a cyclase, which is defective in strain C9, as well as other enzymes.
Mechanism of the Enhancement of the Bohr Effect in Mammalian Hemoglobins by Diphosphoglycerate
Authors: Riggs Austen
Published: May 2006

The number of protons released from several mammalian hemoglobins as a consequence of oxygenation is greater in the presence of low concentrations of 2,3-diphosphoglycerate than in its absence. A mechanism for this enhancement of proton release is proposed. The basis of this mechanism is that 2,3-diphosphoglycerate binds primarily between the protonated α-NH
2
terminal groups of the two β chains in deoxyhemoglobin. This binding will shift the ionization equilibria in favor of the protonation of the deoxyhemoglobin. Partial release of 2,3-diphosphoglycerate upon oxygenation of the hemoglobin is then accompanied by a release of protons. The apparent enthalpy of diphosphoglycerate binding appears to be close to zero. The previously reported temperature dependence appears to be due entirely to the associated protonation reaction. If only a single diphosphoglycerate binding site is assumed, the intrinsic association constant is estimated to be 3.9 × 10
5
M
-1
for deoxyhemoglobin and 1.05 × 10
4
M
-1
for oxyhemoglobin at 20°C in 0.1 M NaCl.
Determination of Distance Distribution Functions by Singlet-Singlet Energy Transfer
Authors: Cantor Charles R. , Pechukas Philip
Published: May 2006

The efficiency of energy transfer between two chromophores can be used to define an apparent donor-acceptor distance, which in flexible systems will depend on the
R
0
of the chromophores. If efficiency is measured as a function of
R
0
, it will be possible to determine the actual distribution function of donor-acceptor distances. Numerical procedures are described for extracting this information from experimental data. They should be most useful for distribution functions with mean values from 20-30 Å (2-3 nm). This technique should provide considerably more detailed information on end-to-end distributions of oligomers than has hitherto been available. It should also be useful for describing, in detail, conformational flexibility in other large molecules.
Enhanced Release of Dopamine-β-Hydroxylase from Sympathetic Nerves by Calcium and Phenoxybenzamine and Its Reversal by Prostaglandins
Authors: Johnson David G. , Thoa Nguyen B. , Weinshilboum Richard , Axelrod Julius , Kopin Irwin J.
Published: May 2006

Dopamine-β-hydroxylase (EC 1.14.2.1), an enzyme localized in sympathetic synaptic vesicles, was released together with norepinephrine during
in vitro
stimulation of the hypogastric nerve that innervates the vas deferens of the guinea pig. Stimulation of the nerve in the presence of high concentrations of calcium (7.5 mM) or phenoxybenzamine caused a marked increase in the amounts of the enzyme and norepinephrine released into the bath. The augmentation of release of dopamine-β-hydroxylase by 7.5 mM calcium or phenoxybenzamine was reversed by prostaglandin E
2
. These findings suggest that the release of the sympathetic neurotransmitter, norepinephrine, occurs by a process of exocytosis in which the vesicular content of soluble dopamine-β-hydroxylase is also released. The depolarization-induced exocytosis, which is stimulated by calcium, may be affected by prostaglandin E
2
or phenoxybenzamine through inhibition or enhancement of the actions of calcium in the release process.
Adenosine 3′:5′-Cyclic Monophosphate Concentration in the Bacterial Host Regulates the Viral Decision between Lysogeny and Lysis
Authors: Hong Jen-Shiang , Smith Gerald R. , Ames Bruce N.
Published: May 2006

Mutants of
Salmonella typhimurium
defective in adenylate cyclase (
cya
gene) or in cAMP receptor protein (
crp
gene) are lysogenized at reduced frequency by phage P22. One class of the bacterial mutants with an altered RNA polymerase (
rif
gene) is also lysogenized at reduced frequency. In the three types of mutant bacteria, the phage's decision between lysogeny and lysis is shifted to lysis and the phage form clear plaques. We propose that in wild-type bacteria the cAMP-receptor protein, in combination with cAMP, activates bacterial RNA polymerase to transcribe certain phage genes that are required for efficient lysogenization. Under conditions of strong catabolite repression, when the supply of energy and biosynthetic components is abundant and the concentration of cAMP is low, the phage would multiply and lyse the cell. When the supply of energy is deficient and the concentration of cAMP is high, the phage would lysogenize the cell.

Phage mutants have been isolated that form turbid plaques on the three classes of bacterial mutants due to a higher frequency of lysogeny. These phage mutants have been shown by complementation to be defective in the same gene, which we have called the
cly
gene. These
cly
mutants lysogenize the wild-type bacteria with a 99% frequency and, thus, do not form plaques on them.

Other kinds of bacterial mutants are also lysogenized at reduced frequency by phage P22. They may be altered in other physiological control systems that influence the frequency of lysogenization.
Selective Condensation of Aminoacyl Adenylates by Nucleoproteinoid Microparticles
Authors: Nakashima Tadayoshi , Fox Sidney W.
Published: May 2006

Microparticles composed of each of four enzymically synthesized homopolynucleotides and the same lysine-rich proteinoid have been found to influence the condensation of the AMP-anhydrides of each of four amino acids. The conditions of preparation of the particles and other variables of the experiments control the types of reaction. When a specified set of conditions was identified empirically, the incorporation favored the amino acids whose present-day codons are related to the homopolynucleotide in the particle.
The Role of X-Chromosome Inactivation during Spermatogenesis
Authors: Lifschytz Eliezer , Lindsley Dan L.
Published: May 2006

Inactivation of the single X chromosome in the primary spermatocytes of species with heterogametic males is postulated as a basic control mechanism on the chromosomal level that is required for normal spermatogenesis. This view is supported by (
a
) cytological observations of X-chromosome allocycly in the primary spermatocytes of all male-heterogametic organisms that were adequately examined, (
b
) autoradiographic evidence of early cessation of transcription by the X chromosome in the mouse and three species of grasshopper, and (
c
) the male sterility of animals with certain X-chromosome rearrangements that cannot be attributed to misfunction of specific genes. X-chromosome inactivation during spermatogenesis is proposed as the ideal system for studies of genetic control at the chromosomal level.
Methylation of Cytosine Residues in DNA Controlled by a Drug Resistance Factor
Authors: Hattman Stanley , Gold Edward , Plotnik Alan
Published: May 2006

The proportion of 5-methylcytosine (5MeCyt) and 6-methylaminopurine (
N
6
-methyladenine, 6MeAde) in bacteriophage P22 DNA was analyzed as a function of the host-specificity the phage carried. In the DNA of P22 grown in strains harboring the modifying drug-resistance-transfer-factor N-3, the 5MeCyt content was at least twice that after growth in strains lacking the factor. In contrast, the 6MeAde level of P22 DNA was unaffected by the presence or absence of the factor. The 6MeAde and 5MeCyt levels were unaffected by factors 222 and N-1, which do not modify phage DNA.

The 5MeCyt/6MeAde ratio was only slightly higher in the DNA of
Salmonella
strains that had received the N-3 factor. After transfer of the N-3 factor to
Escherichia coli
strain B, which normally lacks 5MeCyt, a high content of 5MeCyt is observed. We conclude that the N-3 factor controls a DNA methylase specific for cytosine residues. If the N-3 host specificity is imparted by cytosine methylation, this would be the first instance where a biological role for 5MeCyt has been elucidated.
Cell Separation on Affinity Columns: The Isolation of Immunospecific Precursor Cells from Unimmunized Mice
Authors: Henry Claudia , Kimura John , Wofsy Leon
Published: May 2006

We have used affinity columns to isolate from the spleens of unimmunized mice a population of lymphocytes that specifically bind a lactoside hapten. These cells are able to initiate an antibody response to azophenyl-β-lactoside when transferred to appropriate irradiated recipients.
Matching Sequences under Deletion/Insertion Constraints
Authors: Sankoff David
Published: May 2006

Given two finite sequences, we wish to find the longest common subsequences satisfying certain deletion/insertion constraints. Consider two successive terms in the desired subsequence. The distance between their positions must be the same in the two original sequences for all but a limited number of such pairs of successive terms. Needleman and Wunsch gave an algorithm for finding longest common subsequences without constraints. This is improved from the viewpoint of computational economy. An economical algorithm is then elaborated for finding subsequences satisfying deletion/insertion constraints. This result is useful in the study of genetic homology based on nucleotide or amino-acid sequences.
Anti-Insulin Actions of a Bovine Pituitary Diabetogenic Peptide on Glycogen Synthesis
Authors: Miller Thomas B. , Larner Joseph
Published: May 2006

The site(s) of action of a bovine pituitary diabetogenic peptide that produces hyperglycemia and hyperinsulinemia
in vivo
(dogs or humans) was investigated
in vitro
. When rat diaphragms were incubated with the peptide in the presence of insulin, the peptide depressed insulin-mediated (
a
) glucose uptake, (
b
) glycogen synthesis, and (
c
) glycogen synthase activation (conversion of
D
to
I
form). Incubation with the peptide alone resulted in small increases in (
a
), (
b
), and (
c
). Insulin-mediated glycogen synthase kinase inactivation was inhibited when both insulin and peptide were present (
d
), whereas glycogen synthase kinase activity was lowered by the peptide alone. High doses of insulin completely reversed inhibitory effects of the peptide on glycogen synthesis. Therefore, the hyperglycemic and anti-insulin properties of this peptide
in vivo
can possibly be explained by the partial blocking action of the peptide on insulin-mediated glucose uptake and glycogenesis.
Uncoupling of the
recBC
ATPase from DNase by DNA Crosslinked with Psoralen
Authors: Karu Alexander E. , Linn Stuart
Published: May 2006

Exonucleolytic cleavage of DNA by the
recBC
DNase is accompained by a DNA-dependent ATP hydrolysis that ceases when the DNA that has been digested to a limit. On the other hand, DNA that has been crosslinked by 4,5′,8-trimethylpsoralen in the presence of 360-nm light remains an effective cofactor in the ATPase reaction, but is resistant to digestion by the enzyme. Psoralentreated DNA is degraded by pancreatic DNase, micrococcal nuclease, and
Escherichia coli
B restriction enzyme, but not by
Neurospora crassa
nuclease, suggesting that crosslinking did not grossly distort the duplex structure of the DNA. The psoralen-DNA is not a potent inhibitor, but competes with single-stranded DNA from bacteriophage fd for the
recBC
DNase to roughly the same extent as does normal duplex DNA. DNA treated with psoralen in the dark, exposed to 360-nm light in the absence of psoralen, or treated with the intercalating agents ethidium bromide, 9-aminoacridine, ICR-191, or actinomycin D, responds to the enzyme no differently from untreated DNA. However, DNA crosslinked with mitomycin C or nitrogen mustard behaves similarly to psoralen-treated DNA. The relationship of these findings to models for the function and control of the
recBC
ATPase and nuclease, and the advantages of psoralen as a DNA crosslinking agent, are discussed.
Mechanism of Hormonal Induction of Tyrosine Aminotransferase Studied by Measurement of the Concentration of Growing Enzyme Molecules
Authors: Scott Walter A. , Shields Robert , Tomkins Gordon M.
Published: May 2006

Proteins labeled in cultured hepatoma cells grown in the presence of radioactive amino acids and pactamycin consist primarily of growing polypeptide chains initiated before addition of the antibiotic. Nascent tyrosine aminotransferase (EC 2.6.1.5) molecules were labeled in this way, and their radioactivity after completion was measured immunologically. Cells exposed to the synthetic adrenal steroid, dexamethasone, contain 10- to 18- times as much nascent enzyme as uninduced cells. These results indicate that induction control is not at the level of polypeptide-chain elongation or release, but probably operates on either the amount of messenger RNA or the rate of specific polypeptide-chain initiation.
A Transcribing Activity Induced by Satellite Phage P4
Authors: Barrett Kathleen J. , Gibbs Warren , Calendar Richard
Published: May 2006

Satellite bacteriophage P4 induces a new transcribing enzyme that synthesizes polyriboguanylic acid in the presence of the poly(dG)·poly(dC) homopolymer pair. This transcribing activity was partially purified and shown to be distinct from the host RNA polymerase. Analysis of conditional lethal mutants suggests that this new enzyme is necessary for replication of phage DNA.
Biochemical Characterization and Cytochemical Localization of a Catecholamine-Sensitive Adenylate Cyclase in Isolated Capillary Endothelium
Authors: Wagner Roger C. , Kreiner Peter , Barrnett Russell J. , Bitensky Mark W.
Published: May 2006

Capillaries were isolated from epididymal fat, and a catecholamine-sensitive adenylate cyclase found in these capillaries was characterized. The effect of various hormones on the accumulation of adenosine 3′:5′-cyclic monophosphate in capillary endothelial cells was determined and the cyclase was found to exhibit mixed alpha and beta characteristics. Cyclase was cytochemically localized in these endothelial cells with 5′-adenylyl-imidodiphosphate as a specific cyclase substrate and alloxan as a specific cyclase inhibitor. Lead imidodiphosphate was precipitated at or near the site of cyclase activity upon hydrolysis of 5′-adenylyl-imidodiphosphate by cyclase. This reaction product was observed primarily on the luminal surface of intact capillaries, in micropinocytic invaginations, in free vesicles within the cytoplasm, and in the intracellular junctions.
Cleavage of Bacteriophage f1 DNA by the Restriction Enzyme of
Escherichia coli
B
Authors: Horiuchi Kensuke , Zinder Norton D.
Published: May 2006

We studied the cleavage of the replicative-form DNA (RF I) of bacteriophage f1 and its SB mutants by purified restriction endonuclease of
E. coli
B. The results indicate that: (
i
) Circular replicative forms are broken once to yield full-length linear molecules (RF III). Such linear molecules are less susceptible than RF I to endonuclease R-B. (
ii
) The genetic sites (SB sites) that confer on the DNA susceptibility to B-restriction are not the actual sites of cleavage. The number of possible cleavage sites is larger than the number of SB sites. We conclude this because an RF III molecule produced by endonuclease R-B from RF I of a mutant that has only one SB site can be circularized by denaturation and renaturation. (
iii
) The SB site is not modified when the DNA is cleaved, since an SB site can be used repeatedly by endonuclease R-B; the RF III described in
ii
can be cleaved by the same enzyme after denaturation and renaturation.
Role of Muscarinic Cholinergic Receptors in Regulation of Guanosine 3′:5′-Cyclic Monophosphate Content in Mammalian Brain, Heart Muscle, and Intestinal Smooth Muscle
Authors: Lee Tee-Ping , Kuo J. F. , Greengard Paul
Published: May 2006

Effects of acetylcholine and of agents that mimic or block its physiological actions have been studied upon concentrations of guanosine 3′:5′-cyclic monophosphate (cyclic GMP) and adenosine 3′:5′-cyclic monophosphate (cyclic AMP) in slices of mammalian cerebral cortex, heart ventricle, and ileum. Acetylcholine, and cholinomimetic agents with a predominantly muscarinic action, such as methacholine, bethanechol, and pilocarpine, induced an increase in the concentration of cyclic GMP, accompanied by no change or a slight decrease in the concentration of cyclic AMP, in all three tissues studied. Tetramethylammonium, a cholinomimetic agent with a predominantly nicotinic action, on the other hand, did not significantly alter concentrations of either cyclic GMP or cyclic AMP. The increase in the tissue content of cyclic GMP induced by acetylcholine and its muscarinic analogs was antagonized by atropine, a muscarinic blocking agent, but not by hexamethonium, a nicotinic blocking agent.

These and other results suggest the generalization that the interaction of acetylcholine with muscarinic receptors, but not with nicotinic receptors, causes an increase in the concentration of cyclic GMP. The data are compatible with the hypothesis that cyclic GMP may mediate the muscarinic actions of acetylcholine.

The antagonistic actions of cholinergic and adrenergic agents on the physiology of contraction of intestinal smooth muscle and of cardiac muscle are reflected in, and may result from, antagonistic actions of these compounds on the levels of both cyclic GMP and cyclic AMP in these tissues.
Conformational Relationships Between Analogs of Acetylcholine and Those of Local Anesthetics in Solution
Authors: Makriyannis Alexandros , Sullivan Richard F. , Mautner Henry G.
Published: May 2006

Conformations of analogs of acetylcholine and of related local anesthetics, in which either of the oxygen atoms had been replaced by other heteroatoms, were studied in solution by nuclear magnetic resonance. Several correlations between structure and conformation could be made.
Conformational Energy Studies of Oxytocin and Its Cyclic Moiety
Authors: Kotelchuck David , Scheraga Harold A. , Walter Roderich
Published: May 2006

Conformational energies were calculated for oxytocin in water, starting with a conformation proposed from nuclear magnetic resonance measurements in [
U
-
2
H](CH
3
)
2
SO. Calculations on the isolated ring showed that conformations with one transannular hydrogen bond had the same energies as those without such bonds; those with two such hydrogen bonds do not appear to form. Calculations on the whole molecule also indicated the existence of several low-energy minima in the energy surface, and no preference for hydrogen-bond formation in the cyclic moiety; the hydrogen bond proposed between the Gly peptide NH and the Cys-6 C=O in the acyclic moiety can form. The proposed proximity of the tail to the ring is one of two low-energy conformations found. The Tyr side chain had two conformations of comparable energy, one over the ring between the Gln and Asn side chains, and the other with the Tyr side chain away from the ring. The oxytocin molecule appears to be flexible, and is probably sensitive to changes in its environment.
Partial Characterization of a Tetrodotoxin-Binding Component from Nerve Membrane
Authors: Benzer Theodore I. , Raftery M. A.
Published: May 2006

Tetrodotoxin from Japanese puffer fish has been labeled with tritium and purified from the crude mixture obtained. The interaction between the purified [
3
H]tetrodotoxin and membrane suspensions from the olfactory nerve of long-nosed garfish has been investigated by equilibrium dialysis. Tetrodotoxin binds to membrane suspensions with a dissociation constant

K
D

= 8.3 nM. The nerve preparation binds 42 pmol of [
3
H]tetrodotoxin/g of wet tissue at saturating toxin concentrations. With various hydrolytic enzymes, the binding component is shown to be a protein embedded in a phospholipid environment. The binding is inhibited below pH 4.0 and is not stable towards heat. Tetrodotoxin binding is not inhibited by the local anesthetic, procaine.
Precursors of Collagen Secreted by Cultured Human Fibroblasts
Authors: Goldberg Burton , Epstein Ervin H. , Sherr Charles J.
Published: May 2006

Soluble precursors of collagen (“procollagens”) in the culture medium of human diploid fibroblasts were characterized by molecular sieve chromatography on 6% agarose and by sodium dodecyl sulfate-acrylamide gel electrophoresis. Under the denaturing conditions for gels, the following molecular species were identified: a major species of three procollagen chains, a procollagen dimer, and free procollagen chains. Reduction with 2-mercaptoethanol completely dissociated the trimer and dimer, releasing procollagen α1 and procollagen α2 chains with molecular weights of about 120,000. Both pro α1 and pro α2 chains could be labeled with [
35
S]cystine. In addition, free procollagen chains with molecular weights of less than 120,000, but heavier than native α chains, were identified in gels. Radioactivity in all of the above molecules could be chased into native α chains extracted from extracellular fibers of the cell layers. The data indicate that: (
i
) collagen is secreted as a disulfidestabilized procollagen trimer with the composition, (pro α1)
2
·pro α2; (
ii
) noncovalent interactions maintain the three-chain assembly during stepwise enzymatic excisions of N-terminal, cysteine-containing procellagen peptides; and (
iii
) after such excisions, native helical molecules, (α1)
2
·α2, precipitate as fibers in the cell layers.
Reversible Transformation by Urea of Contact-Inhibited Fibroblasts
Authors: Weston James A. , Hendricks Karen L.
Published: May 2006

200 mM urea elicits alterations of cell social behavior
in vitro
. In the presence of urea, contact inhibition of movement and growth is reduced compared to untreated fibroblastic cell populations. This reduction of contact inhibition is rapidly reversible, but reversal requires some cycloheximide-sensitive cellular process. Cells treated with urea are agglutinable by concanavalin A, suggesting that urea might remove some cell-surface component(s). A nondialyzable factor can, in fact, be detected in the supernatant medium of urea-treated cells. This active constituent appears to be heat-labile and trypsin-sensitive, and can itself restore normal contact-inhibitory behavior to cells maintained in the urea-transformed state by cycloheximide. This system may permit identification and characterization of surface components that are involved in regulating normal cell social behavior.