bluuebunny/crossref_metadata_2025 huggingface dataset:
Presynaptic Neuromuscular Inhibition by Porphobilinogen and Porphobilin
Authors: Feldman Daniel S. , Levere Richard D. , Lieberman James S. , Cardinal Ruth A. , Watson C. J.
Published: May 2006

The rat hemidiaphragm was studied
in vitro
as a test system to evaluate the effects of heme precursors and the uroporphyrins upon neuromuscular excitability. Porphobilinogen and porphobilin had no effect on the
resting
miniature end-plate potential frequency, but the K
+
-augmented frequency was significantly reduced. Porphobilin and porphobilinogen gave 50% of their maximal effect at concentrations of 0.008 and 0.6 μg/ml, respectively; the effect increased with concentration. Uroporphyrin I at 0.05-1.0 μg/ml caused a 25% decrease in frequency, but the effect did not increase with concentration. At similar concentrations, uroporphyrin III was without effect.

The concentrations of porphobilin and porphobilinogen effective in inhibiting the K
+
stimulation, which are several orders of magnitude lower than the effective concentrations of simple amino acids, are those which might reasonably be expected in the sera of patients with acute intermittent porphyria.
Optical Activity of Human Lysozyme
Authors: Halper J. P. , Latovitzki N. , Bernstein H. , Beychok S.
Published: May 2006

The ultraviolet circular dichroism spectra of human lysozyme are presented. Effects of pH and added inhibitor (
N
-acetyl-D-glucosamine) were examined and the results were compared with similar measurements of hen egg-white lysozyme. The near-ultraviolet CD spectral bands are substantially different in the human and hen egg-white enzymes. In addition to marked dissimilarities in the spectral interval 260-300 nm, an unusual CD band occurs at an anomalous wavelength (313 nm) in human lysozyme. The pH dependence of the latter suggests a possible interaction, absent in hen egg-white lysozyme, between a tryptophan and a tyrosine residue. Analysis of the spectra furthermore suggests lesser net rotational strengths of tryptophan bands in hen egg-white lysozyme than in human lysozyme, although the latter has one less tryptophan residue. The relationship between the CD spectra and the sequence differences of the proteins is discussed, as well as the CD spectra (published by others) of a closely related protein, bovine α-lactalbumin. Contributions of cystine residues to the spectra are examined in the light of possible differences in chirality of one of the four disulfide bridges.

The far-ultraviolet CD spectra of human and egg-white lysozyme are quite similar, though not identical. In view of the pronounced differences in side-chain optical activity, and of the effect of pH variation on the far-ultraviolet CD spectrum of human lysozyme, it is likely that at least part of the observed difference in spectra is due to nonpeptide optical activity, and that the proteins have a secondary structure in common.
Subordinate Quadratic Forms and Their Complementary Forms
Authors: Morse Marston
Published: May 2006

Theorem
1. For α, β on the range 1,..., μ, let
Q
(
z
) =
*
a
αβ
z
α
z
β be a real valued, nonsingular, symmetric quadratic form. For positive integers
r
and
s
such that μ =
r
+
s
set (
z
1
,...,
z
μ
) = (
u
1
,...,
u
r
:
S
1
,...,
S
n
),
Q
(
z
) =
P
(
u, s
) and [Formula: see text] Let
B
= (
z
(1)
,...,
z

(
r
)

) be a base “over
R
” for points
z
ε π

r

. For an arbitrary
r
-tuple ω
1
,..., ω

r

set [Formula: see text] index

H
B

(ω) = κ and nullity

H
B

(ω) = ν. Then [Formula: see text]
Mammalian Peptide Chain Termination, II. Codon Specificity and GTPase Activity of Release Factor
Authors: Beaudet Arthur L. , Caskey C. T.
Published: May 2006

In vitro
peptide chain termination with release factor preparations from rabbit reticulocytes, guinea pig liver, or Chinese hamster liver is directed with UAAA, UAGA, or UGAA, suggesting that UAA, UAG, and UGA are terminator condons for mammalian cells. Purified release factor from rabbit reticulocytes has ribosomaldependent GTPase activity, which is stimulated by UAAA. GTP hydrolysis appears requisite for
in vitro
peptide chain termination in mammals.
A Simple, Sensitive Protein-binding Assay for Guanosine 3′:5′-Monophosphate
Authors: Murad Ferid , Manganiello Vincent , Vaughan Martha
Published: May 2006

A protein-binding assay for guanosine 3′:5′-monophosphate, which employs an enzyme preparation from lobster tail muscle, is described. The binding constant for cyclic GMP was 2-10 nM for four different enzyme preparations. The method can be set up in several days and permits the detection of as little as 0.5-1 pmol of cyclic GMP. In some instances, it is possible to assay the nucleotide in urine or deproteinized extracts of tissue without purification. For other samples, a simple method for separating and purifying cyclic AMP and cyclic GMP is described.
Purification and DNA Synthesis in Cell-Free Extracts: Properties of DNA Polymerase II
Authors: Kornberg Thomas , Gefter Malcolm L.
Published: May 2006

The major DNA-synthesizing enzyme present in Pol A
1
-
Escherichia coli
(DNA polymerase II) has been purified to homogeneity as judged by polyacrylamide gel electrophoresis. The enzyme requires all four deoxynucleoside triphosphates, Mg
++
, NH
4
+
, and native DNA for maximal activity. The enzyme activity is sensitive to sulfhydryl reagents and is insensitive to anti-DNA polymerase I antiserum. A second DNA-synthesizing enzyme, present in low amounts, has been identified in Pol A
1
-
extracts. The relationship of this enzyme to DNA polymerases I and II is discussed.
Altered Methylation of Ribosomal RNA in an Erythromycin-Resistant Strain of
Staphylococcus aureus
Authors: Lai C. J. , Weisblum B.
Published: May 2006

In certain strains of
Staphylococcus aureus
, a concentration of erythromycin between 10
-8
and 10
-7
M can induce resistance to concentrations of this drug as high as 10
-4
M. In one such strain studied,
S. aureus
(1206),
N
6
-dimethyladenine is not normally present in 23S rRNA; however, a compound presumptively identified (on the basis of paper chromatography in three different solvents) as
N
6
-dimethyladenine appears in the 23S rRNA of growing cells that have been incubated in a medium containing 10
-7
M erythromycin. It has been shown previously that the induction of the erythromycin-resistant phenotype that occurs under these conditions requires 10
-8
-10
-7
M erythromycin for maximal expression within 1 hr and that induction results in modified 50S ribosomal subunits, which are then unable to bind erythromycin or lincomycin. Methylated adenine is also found in the 16S rRNA from the strain of
S. aureus
studied; however, in contrast to the situation with 23S rRNA, the amount in 16S rRNA is not affected by erythromycin. These findings provide the first example of a correlation between the methylation of rRNA and altered ribosomal function.
Solid-Phase Synthesis with Attachment of Peptide to Resin through an Amino Acid Side Chain: [8-Lysine]-Vasopressin
Authors: Meienhofer Johannes , Trzeciak Arnold
Published: May 2006

It is proposed that the scope of solid-phase peptide synthesis could be considerably broadened by attaching peptides to the solid-phase through functional side-chain groups rather than through the commonly used α-carboxyl groups. Side-chain attachment offers the use of a large variety of chemical linkages to solid supports. Attachment through the ε-amino group of the lysine residue to a polystyrene resin has been applied to a solid-phase synthesis of lysine-vasopressin.
N
α
-
tert
-butyl-oxycarbonyl-L-lysyl-glycinamide was condensed with chloroformoxymethyl polystyrene-2% divinylbenzene resin. After removal of the
N
α
-protecting
tert
-butyloxycarbonyl group, the peptide chain was elongated by standard Merrifield procedures to give Tos-Cys(Bzl)-Tyr-Phe-Glu-(NH
2
) - Asp(NH
2
) - Cys(Bzl) - Pro - Lys(Z - resin) - Gly-NH
2
. Cleavage from the resin with HBr in dioxane or trifluoroacetic acid gave a partially protected nonapeptide hydrobromide. For purification, it was converted into a fully protected peptide by treatment with benzyl
p
-nitro-phenyl carbonate and crystallized. Deprotection by sodium in liquid ammonia, oxidative cyclization, IRC-50 desalting, and ion-exchange chromatography gave lysinevasopressin with high potency in a rat-pressor assay.
An Enzyme-Based Theory of Obligate Anaerobiosis: The Physiological Function of Superoxide Dismutase
Authors: McCord Joe M. , Keele Bernard B. , Fridovich Irwin
Published: May 2006

The distribution of catalase and superoxide dismutase has been examined in various micro-organisms. Strict anaerobes exhibited no superoxide dismutase and, generally, no catalase activity. All aerobic organisms containing cytochrome systems were found to contain both superoxide dismutase and catalase. Aerotolerant anaerobes, which survive exposure to air and metabolize oxygen to a limited extent but do not contain cytochrome systems, were found to be devoid of catalase activity but did exhibit superoxide dismutase activity. This distribution is consistent with the proposal that the prime physiological function of superoxide dismutase is protection of oxygen-metabolizing organisms against the potentially detrimental effects of the superoxide free radical, a biologically produced intermediate resulting from the univalent reduction of molecular oxygen.
Phosphorylation of Ribosome-Associated Protein by an Adenosine 3′:5′-Cyclic Monophosphate-Dependent Protein Kinase: Location of the Microsomal Receptor and Protein Kinase
Authors: Walton Gordon M. , Gill Gordon N. , Abrass Itamar B. , Garren Leonard D.
Published: May 2006

In the adrenal cortex, the adenosine 3′:5′-cyclic monophosphate (cAMP)-receptor protein and the cAMP-dependent protein kinase are located in both the cytosol and endoplasmic reticulum. The cAMP-dependent protein kinase from the cytosol catalyzes the phosphorylation of ribosome-associated protein. Ribosomes washed in 0.5 M NH
4
Cl retain the substrate of the protein kinase reaction, but are dependent on the NH
4
Cl extract for
in vitro
protein synthesis. Dissociation of the 80S ribosomes by 0.88 M KCl, however, releases the ribosome-associated (protein) substrate of the phosphorylation reaction.
Localization of a Portion of the Ribosomal RNA Genes in
Escherichia coli
Authors: Birnbaum Linda S. , Kaplan Sam
Published: May 2006

About one-half of the genes coding for ribosomal RNA in
Escherichia coli
have been localized by the use of F-merogenotes. These cistrons have been positioned between 74 and 77 min on the
E. coli
map described by Taylor and Trotter. The episomal DNA carrying these genes was enriched by chromatography. The map position is discussed with reference to previous localization attempts.
Conformation of Cyclolinopeptide A Observed by Circular Dichroism
Authors: Naider Fred , Benedetti Ettore , Goodman Murray
Published: May 2006

A stereochemical investigation, by circular dichroism, of a synthetic nonapeptide (cyclolinopeptide A) in several organic and organic-sulfuric acid solvents is presented. From this examination, and results found for a conformationally rigid model compound, 1,7,7-trimethyl-3-azabicyclo [2.2.1] heptan-2-one(camphorolactam), it is concluded that cyclolinopeptide A may exist in several conformations in solution. None of these conformations is believed to be stabilized by intramolecular hydrogen bonds. Some details on an x-ray analysis of the cyclic nonapeptide are also presented.
Identification of the Mouse Karyotype by Quinacrine Fluorescence, and Tentative Assignment of Seven Linkage Groups
Authors: Miller O. J. , Miller D. A. , Kouri R. E. , Allderdice P. W. , Dev V. G. , Grewal M. S. , Hutton J. J.
Published: May 2006

A karyotype of the mitotic chromosomes of the house mouse has been prepared based upon quinacrine fluorescence patterns. All 19 pairs of autosomes and the X and Y chromosomes have been identified. Examination of the chromosomes of the following translocation stocks, T(11;?)1Ald, T(3;?)6Ca, T(2;9)138Ca, T(2;12)163H, and T(9;13)190Ca, have led to the tentative assignments of autosomal linkage groups (LG) to chromosomes as follows: LGII to chromosome number 10 (or 13), LGIII to 12 or 15, LGIX to 16, LGXI to 6, LGXII to 19 and LGXIII to 1. By definition, LGXX is on the X chromosome.
Independent Folding of the Variable and Constant Halves of a Lambda Immunoglobulin Light Chain
Authors: Björk I. , Karlsson F. A. , Berggård I.
Published: May 2006

Optical rotatory dispersion and circular dichroism studies of a lambda immunoglobulin light chain and its variable and constant halves are reported. The two fragments, which have been extensively characterized, were isolated after proteolytic digestion of the λ-chain. A dichroism band at 217 nm, previously found to be characteristic of all immunoglobulins, was given by both the variable and constant halves. In other respects, the fragments yielded clearly different spectra, reflecting differences in their conformations. Comparisons of the theoretical curves calculated for an equimolar mixture of the fragments with the corresponding curves measured for the λ-chain showed that most of the minimal conformational changes accompany cleavage of the polypeptide into its halves. This suggests that in the intact light chain, the variable and constant parts exist as independently folded regions.
Are Cytoplasmic Microtubules Heteropolymers?
Authors: Bryan Joseph , Wilson Leslie
Published: May 2006

Colchicine-binding protein, considered to be microtubule protein, was purified from chick embryo brain by column chromatography in one step on DEAE-Sephadex. The active colchicine-binding unit is a dimer, MW 115,000 ± 5000, which is composed of two nonidentical monomeric units. The two subunits are separable by urea-acrylamide gel electrophoresis after they have been reduced and acetylated. Sodium dodecyl sulfate-acrylamide gel electrophoresis indicates that the subunits both have molecular weights of 55,000 ± 2000. The amino-acid compositions of the two subunits showed statistically significant differences in six amino-acid residues. These results indicate that colchicine-sensitive cytoplasmic microtubules are heteropolymers.
Structure of Concanavalin A at 4 Å Resolution
Authors: Quiocho Florante A. , Reeke George N. , Becker Joseph W. , Lipscomb William N. , Edelman Gerald M.
Published: May 2006

Concanavalin A, a phytohemagglutinin isolated from the jack bean, crystallizes at pH 6.8 in the orthorhombic space group 1222 with
a
= 89.9,
b
= 87.2, and
c
= 63.1 Å. We have analyzed x-ray diffraction intensity data to 4 Å resolution on native concanavalin A and five heavy-metal derivatives: lead, mersalyl, chloroplatinate, uranyl, and
o
-mercuri-
p
-nitrophenol. Heavy-atom positions, occupancies, and isotropic thermal parameters have been refined by least-squares methods.

The electron density maps clearly show the molecular shape and the packing of the concanavalin A molecules. The asymmetric unit (mol wt 27,000) forms an elliptical dome or “gumdrop” with a base of approximately 46 × 26 Å and a height of 42 Å. The subunits are paired across 2-fold axes parallel to the
c
-axis to form dimers. The dimers are in turn paired across points of D
2
symmetry to form tetramers of roughly tetrahedral shape. Each unit has a depression located on the surface which could be the site of saccharide binding. In many regions we have been able to trace the course of the polypeptide chain.
Stimulation of DNA-Dependent RNA Synthesis by a Protein Associated with Ribosomes
Authors: Mahadik S. P. , Srinivasan P. R.
Published: May 2006

A protein factor partially purified from ribosomes of
Escherichia coli
RC
rel
cells starved for an amino acid markedly stimulates DNA-dependent RNA synthesis by core and whole RNA polymerase. This protein factor appears to differ from the sigma factor and the M factor. The properties of this new factor and its mechanism of action have been explored.
Mutational and Physiological Enhancement of Photosynthetic Energy Conversion in
Rhodopseudomonas capsulata
Authors: Lien Stephen , Pietro Anthony San , Gest Howard
Published: May 2006

Photosynthetic growth of
Rhodopseudomonas capsulata
, a nonsulfur purple bacterium, is severely inhibited by inorganic arsenate when this anion is present equimolar to orthophosphate in the culture medium. Studies on an arsenate-resistant mutant indicate that its resistance can be explained by a significantly increased photophosphorylation capacity of the energy-converting machinery, which can compensate for the decrease in adenosine triphosphate regeneration rate caused by esterification of arsenate in place of phosphate. Repeated subculture of the mutant in the presence of arsenate, under certain conditions, yields cell populations that have strikingly elevated contents of membrane-bound reaction-center bacteriochlorophyll, cytochromes, and photo-phosphorylation coupling factor. Membranes from such cells show unusually high photophosphorylation activity, and can be expected to provide a useful experimental material for more refined analysis of the mechanism of the energy-conversion process.
Autoinhibition of Acetylcholine Binding to
Torpedo
Electroplax; A Possible Molecular Mechanism for Desensitization
Authors: Eldefrawi M. E. , O'Brien R. D.
Published: May 2006

Binding of [
3
H]acetylcholine (measured by equilibrium dialysis) to a particulate preparation of
Torpedo
electroplax exhibits autoinhibition at concentrations higher than 1 μM. It is suggested that autoinhibition results from acetylcholine binding to regulatory sites on its receptor macromolecules. This binding causes the change to a new and inactive conformation and rejection of acetylcholine bound to the larger number of active sites. The relationship to the physiological phenomenon of desensitization is discussed.
Tunnel Model for Hard-Sphere Bosons in Their Ground State
Authors: Henderson Douglas
Published: May 2006

In the tunnel model, a fluid is regarded as being composed of rows of molecules, which move almost in one dimension along lines or tunnels, the walls of which are formed by neighboring rows of molecules. This model provides a simple and reliable theory for a classical system of dense hard spheres. The tunnel model has also been applied to quantum hard spheres. However, until recently, there have been no reliable results for dense quantum hard spheres, so that the accuracy of the quantum tunnel model could not be judged. Comparison with a recent variational determination of the ground-state energy of a system of hard spheres shows that the tunnel model is reliable for this system.
Pure-Strain and Genetically Mosaic Liver Tumors Histochemically Identified with the β-Glucuronidase Marker in Allophenic Mice
Authors: Condamine Hubert , Custer R. Philip , Mintz Beatrice
Published: May 2006

A histochemical procedure for β-glucuronidase has been used to make visible the cellular genotypes of liver tumors and of surrounding normal liver clones in allophenic mice. The animals had lifelong genetic mosaicism for cells with the allele for low β-glucuronidase activity (
g/g
genotype, C3H strain) and cells with the allele for high activity (
G/G
genotype, C57BL/6 or BALB/c strain). The former strain is also hepatoma-susceptible; both the latter are nonsusceptible. Of 12 “spontaneous” hepatomas examined, nine were entirely of susceptible-strain hepatic cells and one was of the nonsusceptible strain; the pure-strain tumors usually arose in a liver environment containing clones of each genotype. The cells therefore behave largely autonomously with respect to gene control of tumor susceptibility. However, two tumors with malignant cells of both genotypes were formed, which suggests some measure of intercellular transmission of tumor information. Alternatively, transformation might have occurred in two or more cells concurrently. Mosaic tumors in either case imply that even a hepatoma of one inbred strain, whether in a single-genotype animal or an allophenic mouse, may comprise diverse clones of transformed cells. Possibly many or all hepatomas may therefore be genetically complex entities.
Involvement of Threonine Deaminase in Multivalent Repression of the Isoleucine-Valine Pathway in
Saccharomyces cerevisiae
Authors: Bollon Arthur P. , Magee P. T.
Published: May 2006

A strain (MAR33) of
Saccharomyces cerevisiae
containing a threonine deaminase [L-threonine hydrolyase (deaminating) EC 4.2.1.16] with decreased feedback sensitivity has been shown to have a specific activity of acetohydroxy acid synthetase higher than that of the parent strain (MD11) when both are grown on minimal medium. When strain MAR33 is grown on minimal medium supplemented only with isoleucine, the specific activity of the synthetase is reduced to that found in the parent strain. Another strain, D106-1A, contains a nonsense mutation in the middle of the gene for threonine deaminase. When this strain is grown on minimal medium containing appropriate supplements (which include a nonrepressing concentration of isoleucine), or on minimal medium supplemented with isoleucylglycine (which acts as a limiting source of isoleucine), acetohydroxy acid synthetase remains repressed. Leucine limitation causes partial derepression. With the reversion of the nonsense mutation, either intragenically or via a suppressor for the mutation, partial derepression of the synthetase returns. When D106-1A is diploidized with either M15, a mutant lacking the synthetase, or MD9, a strain containing the enzyme, normal, partially derepressed, values for this enzyme are found. This indicates that threonine deaminase is necessary for derepression, and that it possibly acts as an inducer.
Absolute Configuration of Cecropia Juvenile Hormone
Authors: Meyer Andre S. , Hanzmann Edith , Murphy Robert C.
Published: May 2006

The absolute configuration of the predominant Cecropia hormone, methyl 12,14-dihomojuvenate, has been determined to be methyl (
E,E
)-(10
R
,11
S
)-(+)-10,11-epoxy-7-ethyl-3,11-dimethyl-2, 6-tridecadienoate (I). The less abundant hormone, methyl 12-homojuvenate, can be presumed by analogy to have the corresponding 3,7,11-trimethyldienoate structure (II). The assignment has been established with microamounts of substance by applying Horeau's method to the glycol derivative (III) of the hormone.

The course of the perchloric acid-catalyzed epoxide ring opening of I was checked by conducting the conversion in
18
O-labeled water. It has been ascertained that the configuration at the secondary hydroxyl group of the resulting III remained unchanged. On the other hand, the hydration proceeded with a surprisingly high rate of
cis
opening.
Synthesis and Secretion of Gammaglobulin by Lymph Node Cells: The Acquisition of Carbohydrate Residues of Immunoglobulin in Relation to Interchain Disulfide Bond Formation
Authors: Sutherland Earl W. , Zimmerman Daniel H. , Kern Milton
Published: May 2006

Acquisition of carbohydrates in the disulfide-linked heavy (H) and light (L) chain molecules of murine myeloma (ADJPC5), i.e., HH, HHL, and LHHL, was investigated. That some mannose and glucosamine residues are acquired by immunoglobulin precursor molecules was demonstrated by the detection of glucosamine and mannose in HH, HHL, and LHHL. In contrast, galactose was observed solely in LHHL molecules, which have an identical electrophoretic mobility to the secreted product. Furthermore, as judged from cells incubated with [
3
H]leucine, the more juvenile molecules HH and HHL were predominant in the rough microsome fraction, whereas LHHL was the principal molecular species in the smooth microsome fraction.

Findings of this type were not observed in rabbit lymph node cells. Thus, galactose, as well as mannose and glucosamine, were found in the more juvenile molecule known for this species (HL). Moreover, the ratio of HL:LHHL, as judged from cells incubated with [
3
H]leucine, was about the same in rough and smooth microsomes.
Preparation of Dialyzable Histocompatibility Antigen from BALB/c Mice
Authors: Kerman Ronald H. , Harris T. N. , Harris Susanna
Published: May 2006

Histocompatibility antigens solubilized from cell-membrane fragments of BALB/c mouse spleen and liver, by Triton X-100 and butyl alcohol, were subjected to digestion by proteolytic enzymes in an effort to obtain smaller molecular species that retained antigenic activity. Digestion with both trypsin and papain yielded two antigens of smaller molecular weights that retained the specificity of BALB/c histocompatibility antigen, as determined by the inhibition of allogeneic antibodies, agglutination of BALB/c erythrocytes, adsorption-hemagglutination versus the soluble histocompatibility antigen, and suppression of the ability of BALB/c spleen cells to produce hemolytic plaques to sheep erythrocytes. The two active products of trypsin digestion were, respectively, excluded by Sephadex G-50 but not by G-75, and excluded by G-25 but not by G-50. Papain digestion yielded one active antigen that was excluded by G-25 but not by G-50, and a smaller antigen that was excluded by G-10 but not by G-15 and, as determined by gel filtration, has a molecular weight slightly lower than vitamin B
12
.
Binding of Thyrotropin-Releasing Hormone to Plasma Membranes of Bovine Anterior Pituitary Gland
Authors: Labrie Fernand , Barden Nicholas , Poirier Guy , De Lean Andre
Published: May 2006

An assay for the binding of [
3
H]thyrotropin-releasing hormone ([
3
H]TRH) is described. Plasma membranes isolated from bovine anterior pituitary gland bind about 600 femtomoles of this hormone per mg of protein, as compared to 15 femtomoles per mg of protein in the total adenohypophyseal homogenate (40-fold purification). The equilibrium constant of membrane receptor-[
3
H]TRH binding at 0°C is 4.3 × 10
7
L·M
-1
, or a half-maximal binding of this hormone at 23 nM. The binding is time-dependent; addition of unlabeled hormone induces dissociation of the receptor-[
3
H]TRH complex with a half-life of 14 min. The binding of TRH is not altered by 10 μM melanocyte-stimulating hormone-release inhibiting hormone, lysine-vasopressin, adrenocorticotropin, growth hormone, prolactin, luteinizing hormone, insulin, glucagon, L-thyroxine, or L-triiodothyronine. K
+
and Mg
++
increase formation of the receptor-TRH complex at optimal concentrations of 5-25 mM and 0.5-2.5 mM, respectively, with inhibition at higher concentrations. Ca
++
inhibits binding of TRH at all concentrations tested.
Kinetics of the Reduction of Metalloproteins by Chromous Ion
Authors: Dawson J. W. , Gray H. B. , Holwerda R. A. , Westhead E. W.
Published: May 2006

The reduction of Cu(330) in
Rhus vernicifera
laccase by chromous ion is 30% faster than reduction of Cu(614) at room temperature [pH 4.8, μ = 0.1 (NaCl)], and two parallel first-order paths, attributed to heterogeneity of the protein, are observed at both wavelengths. The reactions of stellacyanin, spinach and French-bean plastocyanins, and cytochrome
c
with chromous ion under similar conditions are faster than that with laccase by factors of 10
2
to 10
4
, and are first order in protein concentration. Comparison of rates and activation parameters for the reduction of “blue” copper in laccase, stellacyanin, and the two plastocyanins indicates that reduction of the Cu(614) site in laccase may occur by intramolecular electron transfer from one of the Cu(330) sites. Our value of ΔH‡ (17.4 kcal/mol) for the chromous ion reduction of cytochrome
c
is consistent with a mechanism in which major conformational changes in the protein must accompany electron transfer.
Specification of Positional Information in Retinal Ganglion Cells of
Xenopus:
Stability of the Specified State
Authors: Hunt R. K. , Jacobson Marcus
Published: May 2006

In the normal development of retinotectal connections, the site in the tectum at which an optic fiber synapses is related to the position of its ganglion-cell body in the retina. How and when the ganglion cells acquire information about their positions is unknown, but the positional information that each ganglion cell will ultimately act upon is determined or specified at embryonic stages 28-32 in the clawed frog,
Xenopus laevis
. Here we report that once positional information has been so specified, it remains stable when the eye is “back-grafted” into the orbit of a stage-28 host, or cultured
in vitro
for up to 10 days before grafting into the orbit of a stage-38 host. Thus, the ganglion cells of these eyes form tectal connections appropriate to their
original
positions in the donor orbits and independent of their final positions in the host orbits. We conclude that specification of positional information involves stable changes in the phenotypic properties of the differentiating retinal cells that (
i
) render the cells refractory to information about changes in their positions after stage 32 and (
ii
) commit each ganglion cell to the development of a unique property (locus specificity) that predisposes its axon to synapse at a particular locus in the retinotectal map.
Note on the Convergence of Sequences of Rational Functions of Best Approximation to a Meromorphic Function
Authors: Walsh Joseph L.
Published: May 2006

If the function
f
(
z
) is meromorphic at every finite point of the plane, analytic on
C
: [unk]
z
[unk] ≤ 1, there are results that can be established concerning the convergence of the sequence

R
n

(
z
) of rational functions of each degree
n
of best approximation to
f
(
z
) on
C
. However, we need to assume certain additional conditions on the convergence of the sequence

R
n

(
z
) itself. The results generalize to more general sets
C
and to more general functions.
Addition of Chemical and Osmotic Free Energies Through Negative Interaction of Protein-Bound Ligands
Authors: Weber Gregorio
Published: May 2006

Simple free energy considerations show that an effector ligand, Y, bound to a protein can modify the standard free energy change of the reaction
P
-
X
+
D
-
R
=
P
-
R
+
D
-
X
, where
P
is a protein,
D
-
R
a small molecule, and
X
a group in the protein that interacts negatively with
Y
. By consideration of a three-compartment system containing the protein, an
X
-acceptor (
A
-
R
), an
X
-donor (
D
-
X
), and the ligand
Y
present at two different concentrations in the inner and outer compartments, it is shown that the protein can perform under steady-state conditions the addition of the free energy in the
Y
concentration gradient to that of the chemical reaction
A
-
X
+
D
-
R
=
A
-
R
+
D
-
X
. This free energy addition can effectively generate a high energy
X
-donor from a low energy one and may be of importance in metabolism, particularly in the oxidative phosphorylation of ADP.
Temperature-Sensitive Mutants of
Escherichia coli
Requiring Saturated and Unsaturated Fatty Acids for Growth: Isolation and Properties
Authors: Harder Mark E. , Beacham Ifor R. , Cronan John E. , Beacham Kathryn , Honegger Joy L. , Silbert David F.
Published: May 2006

A procedure is described for selection of temperature-sensitive mutants affecting fatty-acid synthesis based upon radiation suicide of wild-type organisms by tritiated acetate selectively incorporated into fatty acids. At 37°, two of the mutants extensively incorporate fatty-acid supplements provided in the medium, and grow for extended periods only when a
trans
-unsaturated or a combination of saturated and
cis
-unsaturated fatty acids is available.
In vivo
fatty-acid synthesis, measured by [
14
C]acetate incorporation, is temperature-sensitive in these strains relative to protein synthesis and other non-lipid macromolecular syntheses using acetate. The biochemical nature of these mutations has not been identified.
Formation of Hybrids Between Coliphage λ and Salmonella Phage P22 with a
Salmonella typhimurium
Hybrid Sensitive to These Phages
Authors: Gemski P. , Baron L. S. , Yamamoto Nobuto
Published: May 2006

An unusual
Salmonella typhimurium
hybrid with sensitivity to coliphage λ and salmonella phage P22 has been recovered from matings between an
Escherichia coli
K-12 Hfr donor and an
S. typhimurium
recipient. The hybrid is an excellent host for achieving genetic recombination between λ and P22. Two broad classes of hybrid phages were isolated. The λ-P22 hybrid class, which has the protein coat of λ, contains at least the
c
region of P22. The P22-λ hybrid class has the protein coat of P22 and has inherited at least the
c
marker of λ.
Precursor and Product in Bacteriophage λ Recombination
Authors: Melechen Norman E. , Hudnik-Plevnik T. A.
Published: May 2006

Analyses of the time of recombination in bacteria infected with phage λ and in spheroplasts infected with purified phage λ DNA indicate a preponderance of recombination occurring before replication (“early recombination”) after infection with tandem dimers formed
in vitro
compared to linear monomer DNA and phage infections. Among the early recombinants is a large fraction of cells that produces one recombinant type exclusively. Two suggestions are discussed—that a dimer-like molecule is the precursor of the recombinant progeny molecule and that one recombinant chromosome is the frequent or exclusive product of a recombinational event.
The Role of Polyprenol-Bound Saccharides as Intermediates in Glycoprotein Synthesis in Liver
Authors: Parodi Armando J. , Behrens Nicolas H. , Leloir Luis F. , Carminatti Hector
Published: May 2006

It has been reported that liver microsomes catalyze the transfer of glucose from uridine diphosphate glucose to dolichol monophosphate so as to produce dolichol monophosphate glucose. Dolichol is a polyprenol containing about 20 isoprene units. The glucosyl residue of dolichol monophosphate glucose is transferred to an endogenous acceptor on further incubation with liver microsomes. The glucosylated endogenous acceptor appears to be an oligosaccharide of about 20 monosaccharide units bound to dolichol through a phosphate or pyrophosphate bridge. In this paper it is reported that liver microsomes catalyze the transfer of the oligosaccharide from the glucosylated endogenous acceptor to an endogenous protein. This transfer reaction requires the presence of bivalent cations, manganese being more effective than magnesium. The presence of deoxycholate is also required. Besides the glycoprotein, several water-soluble products are also formed. Preliminary evidence indicates that they are glucose, iligosaccharides of different size, and possibly oligosaccharides bound to amino acids.
Nuclear Magnetic Resonance Spectrum of Deamino-Lysine-Vasopressin in Aqueous Solution and Its Structural Implications
Authors: Dreele P. H. Von , Scheraga H. A. , Dyckes D. F. , Ferger M. F. , Vigneaud V. Du
Published: May 2006

The peaks in the proton nuclear magnetic resonance spectrum of deamino-lysine-vasopressin in aqueous solution at pH values between 3 and 5 were assigned to particular amino-acid residues by use of the results of transfer-of-saturation studies, NH-C
α
H and C
α
H-C
β
H decoupling experiments, and other data. The conformation of deamino-lysine-vasopressin in water differs from that of lysine-vasopressin in the same solvent.
A DNA-Binding Protein in the Serum of Certain Mammalian Species
Authors: Thoburn R. , Hurvitz A. I. , Kunkel H. G.
Published: May 2006

Various mammalian species contain an anionic serum protein that reacts specifically with native DNA. It is considerably less reactive with single-strand DNA and does not react with monodeoxyribonucleotides, homopolyribonucleotides, or duplexes of homopolyribonucleotides. Synthetic dA·dT was an effective inhibitor of the reaction with native DNA, while
Micrococcus luteus
DNA and dG·dC were not inhibitory.

This protein was encountered in the course of studies on DNA antibodies. Although it reacted with red cells coated with DNA and gave agar precipitation bands, it was clearly distinct from DNA antibodies. It was found in the serum of all animals of a given species, migrated as an α-β globulin, and did not crossreact with gammaglobulins. It reacted with DNA in solution to give precipitation curves that were strongly influenced by changes in ionic strength. The protein was isolated from canine serum by precipitation with DNA and purified to homogeneity, as judged by immunochemical and electrophoretic criteria.

A similar protein was found in mink, equine, and other sera, but not in human sera. Previous studies on DNA antibodies in certain experimental animals may have given false positive results due to this protein.
Transfection Mediated by
Mycoplasmatales
Viral DNA
Authors: Liss Alan , Maniloff Jack
Published: May 2006

DNA isolated from
Mycoplasmatales
viruses MVL51 and MVGs51 was infectious when mixed with
Acholeplasma laidlawii
BN1-Na1
R
cells. Infectivity was destroyed by deoxyribonuclease but not by ribonuclease, Pronase, or specific antiserum to the virus. Host mycoplasma cells were only competent for transfection during late-log growth phase. The rates of the establishment of DNase insensitivity of viral DNA transfectants were similar to those of bacteriophage systems. The dose-response curve for transfection suggested that an average of six molecules of DNA must interact with a cell in order to produce one infectious center.
Mycoplasmatales
virus DNA exhibited a low efficiency of infection; one infectious center required 4 × 10
5
virus equivalents of DNA.
Ion-Diffusion Potentials and Electrical Rectification Across Lipid Membranes Activated by Excitation-Induced Material
Authors: Kalkwarf D. R. , Frasco D. L. , Brattain W. H.
Published: May 2006

Membranes synthesized from sphingomyelin-tocopherol mixtures and treated with the protein, “excitation-inducing material,” to increase their electrical conductance were tested for applicability of the Nernst equation and changes in electrical rectifying behavior with temperature. Above pH 7, and in the temperature range 303-323°K, ion-diffusion potentials created by salts of monovalent cations showed that areas of the membrane activated by excitation-inducing material were only permeable to cations. Results also indicated that a parallel current with an activation energy of 1.00 eV per molecule passed through unactivated areas of the membrane. Below pH 7, the ratio of measured diffusion potentials to predicted values decreased steadily.

Electrical rectification was exhibited by membranes activated by excitation-inducing material with positive current consistently passing preferentially from the side rich in excitation-inducing material to the opposite side. For a given membrane, the current-voltage curves did not change from 312 to 323°K; but below 312°K, the membrane suddenly increased its conductance and became ohmic. This phenomenon was independent of salt concentration and pH, and resembled a phase transition.
Binding of Thymus- and Bone Marrow-Derived Lymphoid Cells to Antigen-Derivatized Fibers
Authors: Rutishauser U. , Edelman G. M.
Published: May 2006

Thymus-derived lymphocytes (T cells) and bone marrow-derived lymphocytes (B cells) from mouse spleens bind specifically to antigen-derivatized nylon fibers. The fiber-bound population consisted of about 60%-70% B cells and 30% T cells as determined by cytotoxicity, fluorescence, and antibody-complement binding assays. Essentially all fiber-bound cells were viable and could be accounted for as T or B cells. Enriched populations of T or B cells could be isolated on the fibers by destruction of one or the other cell type with the appropriate antiserum plus complement. T or B cells could also be fractionated according to their relative affinity (or avidity) for a given antigen.
Nonmathematical Models for Evolution of Altruism, and for Group Selection
Authors: Darlington P. J.
Published: May 2006

Mathematical biologists have failed to produce a satisfactory general model for evolution of altruism, i.e., of behaviors by which “altruists” benefit other individuals but not themselves; kin selection does not seem to be a sufficient explanation of nonreciprocal altruism. Nonmathematical (but mathematically acceptable) models are now proposed for evolution of negative altruism in
dual-determinant
and of positive altruism in
tri-determinant
systems. Peck orders, territorial systems, and an ant society are analyzed as examples. In all models, evolution is primarily by individual selection, probably supplemented by group selection. Group selection is
differential extinction
of populations. It can act only on populations preformed by selection at the individual level, but can either cancel individual selective trends (effecting evolutionary homeostasis) or supplement them; its supplementary effect is probably increasingly important in the evolution of increasingly organized populations.
Epstein-Barr Virus: Transformation, Cytopathic Changes, and Viral Antigens in Squirrel Monkey and Marmoset Leukocytes
Authors: Miller George , Shope Thomas , Lisco Hermann , Stitt Daphne , Lipman Muriel
Published: May 2006

Blood leukocytes of two species of new world primates, other than human, transform following exposure to Epstein-Barr virus. The transformed simian cells produce Epstein-Barr virus antigens and infectious (transforming) virus. The simian lymphoblastoid cells form multinucleate giant cells that appear to be selective sites for the production of Epstein-Barr virus. Multinucleate cells reveal intranuclear inclusions; in both species, a large proportion of giant cells contain Epstein-Barr virus antigen detectable by immunofluorescence.
A New Synthetic RNA-Dependent DNA Polymerase from Human Tissue Culture Cells
Authors: Fridlender Bertold , Fry Michael , Bolden Arthur , Weissbach Arthur
Published: May 2006

Two DNA polymerases that can copy synthetic RNA polymers are present in human tissue culture cells. These enzymes which have each been purified about 500-fold, are present in both HeLa cells, which are derived from a cervical carcinoma, and in WI-38 cells, a normal diploid strain originating from human embryonic lung tissue. These synthetic RNA-dependent DNA polymerases are identified by their ability to copy efficiently the ribo strand of synthetic oligonucleotide-homopolymer complexes, and differ in this respect from the known DNA-dependent DNA polymerases found in HeLa cells. The template requirements of these new DNA polymerases resemble that of the RNA-dependent DNA polymerases of the RNA tumor-viruses.
Circular Polarization of Fluorescence of Probes Bound to Chymotrypsin. Change in Asymmetric Environment upon Electronic Excitation
Authors: Schlessinger Joseph , Steinberg Izchak Z.
Published: May 2006

The circular polarization of fluorescence is related to the conformational asymmetry of the emitting molecule in the first singlet excited state in the same way that circular dichroism is related to the conformational asymmetry of the absorbing molecule in the electronic ground state. By measurement of these optical phenomena, the induced asymmetry of two chromophores bound to chymotrypsin (EC 3.4.4.5) when in the ground state was compared with the induced asymmetry of the ligands when in the excited state. The two chromophores studied were 2-
p
-toluidinylnaphthalene-6-sulfonate (TNS), bound at a specific site which is not the active site of the protein, and an anthraniloyl group, bound at the active site of the enzyme. Both chromophores showed a change in induced asymmetry upon electronic excitation, the effect being particularly large in the case of the TNS chromophore. It is thus concluded that the orientation of TNS in the binding site, its freedom of rotation in its site, the strength of binding, or even the site of binding of the dye to the protein might have changed upon electronic excitation.
Covalent Attachment of a Peptidyl-Transfer RNA Analog to the 50S Subunit of
Escherichia coli
Ribosomes
Authors: Pellegrini Maria , Oen Helen , Cantor Charles R.
Published: May 2006

The peptidyl-tRNA analog,
N
-bromo-acetyl-Phenylalanyl-tRNA
Phe
has been prepared. Its binding to the 70S ribosome of
E. coli
is totally dependent upon polyuridylic acid. The analog becomes covalently attached to the 50S particle. It is associated with only one protein fraction after polyacrylamide-gel separation of total 50S proteins. The analog also reacts with 23S ribosomal RNA or a protein that remains tightly bound to this RNA after treatment with LiCl-urea and sodium dodecyl sulfate. The analog can function as a peptidyl-tRNA for at least one peptide transfer, but it then inhibits further chain elongation. This result strongly suggests that this analog becomes covalently bound at the P-site of the ribosome.
Lines That Do Not Increase Their Width Under a Magnifying Glass
Authors: Békésy Georg Von
Published: May 2006

A light beam hitting the retina produces an excitatory process; however, around the edge of the light beam, sensory cells are inhibited and lose their sensitivity. This combination of stimulation and inhibition produces a discrepancy between the luminance pattern presented to the eye and the brightness pattern that is observed. The black and white Mach bands are the best known distortions of this type. It is this interaction that can produce a line that is physically not present in the stimulus, and is different from the usual lines we see.
Formation of Binaries from Triple Systems
Authors: Szebehely Victor
Published: May 2006

The dynamical behavior of three masses moving under their mutual gravitational attraction in a plane is investigated by a systematic series of numerical experiments. It is shown that in 73% of the cases, a triple system disintegrates in less than 150 time units (corresponding to about 150 crossing times), and a binary is formed with the third star that escapes at hyperbolic velocity. The average time for disintegration is of the order of 10
9
years for triple stellar systems, as well as for triple galaxies. The statistics of the escaping masses show that the escaping mass is usually, but not always, the smallest in the system. A simple equation, giving the balance between the negative energy stored in the binary and the positive energy necessary for escape, explains the results qualitatively.
Inhibition of Aggregation and Differentiation of
Dictyostelium discoideum
by Antibodies Against Adenosine 3′:5′-Cyclic Monophosphate Diesterase
Authors: Goidl Edmond A. , Chassy Bruce M. , Love Leslie L. , Krichevsky Micah I.
Published: May 2006

A specific antibody directed against adenosine 3′:5′-cyclic monophosphate diesterase (c-AMP diesterase; EC 3.1.4.c), which is secreted by the amoeboid slime mold,
Dictyostelium discoideum
, was prepared in rabbits. Purified gammaglobulin fractions that contain the antibodies inhibited the activity of cAMP diesterase preparations
in vitro
and interfered with aggregation and development
in vivo
. While cells that were treated with antibody were unable to aggregate because of the inability to destroy cAMP, they aggregated normally when washed free of antibody.
On the Mechanism of Action of Vitamin B
12
. Model Studies. Thermal Rearrangement of Methyl 3,3-Dimethylglycidate to Methyl Levulinate
Authors: Dowd Paul , Nakagawa Christopher S.
Published: May 2006

The discovery that methyl 3,3-dimethylglycidate rearranges to methyl levulinate on heating is discussed in terms of its possible consequences for the mechanism of action of the coenzyme B
12
-dependent enzymes: methylmalonyl-CoA mutase (EC 5.4.99.2), glutamate mutase (EC 5.4.99.1), and
a
-methyleneglutarate mutase. It is also suggested that the proposed mechanism may provide a unifying link between the mechanism of action of the above enzymes and that of the coenzyme B
12
-dependent dioldehydrase and related enzymes.