Showing papers by "Laboratory of Molecular Biology published in 1977"
TL;DR: These cell lineages range in length from one to eight sequential divisions and lead to significant developmental changes in the neuronal, muscular, hypodermal, and digestive systems and are determined by direct observation of the divisions, migrations, and deaths of individual cells in living nematodes.
3,407 citations
TL;DR: The sequence identifies many of the features responsible for the production of the proteins of the nine known genes of the organism, including initiation and termination sites for the proteins and RNAs.
Abstract: A DNA sequence for the genome of bacteriophage phi X174 of approximately 5,375 nucleotides has been determined using the rapid and simple 'plus and minus' method. The sequence identifies many of the features responsible for the production of the proteins of the nine known genes of the organism, including initiation and termination sites for the proteins and RNAs. Two pairs of genes are coded by the same region of DNA using different reading frames.
2,023 citations
TL;DR: FUSION between myeloma cells and spleen cells from immunised donors has been shown to be a successful method of deriving homogeneous anti-SRBC (anti-sheep red blood cell) and anti-TNP antibodies.
Abstract: FUSION between myeloma cells and spleen cells from immunised donors has been shown to be a successful method of deriving homogeneous anti-SRBC (anti-sheep red blood cell) and anti-TNP antibodies1,2. One of the most powerful features of this approach is that, by cloning, one may easily derive cell lines synthesising monoclonal antibodies despite using non-purified immunogens. The multiple components of a heterogeneous population of hybrid cells are resolved by cloning techniques. This feature makes the system a very powerful tool in the study of complex antigenic structures. The established cell lines offer the further advantage of unlimited permanent supply of material, and the possibility of worldwide standardisation.
1,749 citations
TL;DR: This paper reports that autoradiographic sensitivity can be greatly increased for isotopes which emit y rays or high energy p particles by placing a pre-exposed film between the sample and a calcium tungstate X-ray intensifying screen and exposing at --70°C.
843 citations
TL;DR: A new approach to study differentiation antigens by means of monoclonal xenogeneic antibodies produced by myeloma-hybrid lines in culture is described, which allows identification down to minor membrane molecules and also of antigen on small subpopulations of a heterogeneous mixture of cells.
709 citations
TL;DR: Crystals have been obtained of nucleosome cores and analysed by X-ray diffraction and electron microscopy, and a change in the screw of the DNA double helix on nucleosomes formation can be deduced.
Abstract: Cystals have been obtained on nucleosome cores and analysed by X-ray diffraction and electron microscopy. The core is a flat particle of dimensions about 110 X 110 X 57 A, somewhat wedge shaped, and strongly divided into two 'layers', consistent with the DNA being wound into about 1 3/4 turns of a flat superhelix of a pitch about 28 A. The organisation of the DNA can be correlated with the results to enzyme digestion studies. A change in the screw of the DNA double helix on nucleosome formation can be deduced.
653 citations
TL;DR: The structure of sperm whale metmyoglobin has been refined using new intensity data to 2·0 A collected on a four-circle diffractometer starting with the original phase angles determined by isomorphous replacement with heavy atoms.
635 citations
TL;DR: Digestion of rat liver chromatin with micrococcal nuclease at 2°C yields fragments containing multiples of 198±6 base-pairs, which represents the DNA content of a unit of the structure, which suggests an association of H1 with the region of DNA that links adjacent units of theructure.
608 citations
TL;DR: Results suggest that protection of the subfragment-1 site requires the presence of DTNB light chains with intact calcium binding sites, and metal dependence suggests that the flexibility of the two sites is modulated by divalent cations.
594 citations
TL;DR: This work provides the first objective and consistent compilation of α-helix, β-sheet and reverse-turn secondary structure in almost all globular proteins of known tertiary structure.
495 citations
TL;DR: Optimal operating conditions have been sought in relation to zone lengths, filter levels and ill-defined features of the electron density map and consistency of the results suggests that optimal co-ordinates for wellresolved features are located to about 0.1 A.
TL;DR: A cell-free system is described which assembles chromatin from purified DNA in 1 hr under physiological incubation conditions, which converts SV40 DNA to a nucleoprotein which co-sediments with naturally occurring SV40 chromatin and which can be cleaved by micrococcal nuclease to a highly ordered pattern of DNA fragments resembling those from digestion of liver chromatin.
TL;DR: Although these light chains of myosin do not appear to influence the ATP turnover by subfragment-1 alone, they are implicated in interactions involving actin.
TL;DR: The glyceraldehyde 3-phosphate dehydogenase holoenzyme of Bacillus stearothermophilus possesses precise 222 symmetry: in this respect it differs from the reported structure of the lobster muscle enzyme.
Abstract: The glyceraldehyde 3-phosphate dehydogenase holoenzyme of Bacillus stearothermophilus possesses precise 222 symmetry: in this respect it differs from the reported structure of the lobster muscle enzyme. Pairs of active sites are linked through a flexible polypeptide loop which probably mediates the structural changes giving rise to cooperative effects. Three additional salt bridges made by each subunit to others would make a major contribution to thermostability of the tetramer.
TL;DR: Different Fourier maps have revealed one major binding site for each of cobalt and managanese in the presence of magnesium, which is probably involved in the first stage of melting of the tRNA molecule, and may be critical for stabilizing the tertiary structure.
TL;DR: The induction of these two proteins by glucose starvation suggests that they have a role in glucose utilization, and two glucose derivatives, glucosamine and 2-deoxyglucose, are known to interfere with the glycosylation process.
TL;DR: The 5S DNA of Xenopus laevis, coding for oocyte-type 5S RNA, consists of many copies of a tandemly repeated unit of about 700 base pairs, each unit contains a "pseudogene" in addition to the gene.
TL;DR: A developed method is described that is used in establishing the sequence of tyrosine tRNA of Bacillus stearothermophilus and it is described as an attractive experimental system for studying the specific interaction of tRNA and synthetases.
Abstract: METHODS for sequencing nucleic acids have improved significantly in the last few years due to the development of rapid ‘read-off’ gel methods. The first method to be developed was the ‘plus and minus’ copying method for DNA1 and an analogous copying method for RNA now exists2. A different and more direct method for sequencing DNA has been developed3, but no direct method is available for RNA. We have developed such a method and here we describe its use in establishing the sequence of tyrosine tRNA of Bacillus stearothermophilus. This sequence is especially interesting as the tyrosine tRNA and its specific synthetase in B. stearothermophilus offer an attractive experimental system for studying the specific interaction of tRNA and synthetases, which is now possible because of progress in studying the three-dimensional structure of the protein by X-ray crystallography4.
TL;DR: The structure of horse methaemoglobin has been redetermined by phase extension and refinement, which has improved knowledge of the haem geometry and the stereochemistry of the interfaces between the subunits, and confirmed the disorder of the C-terminal residues.
TL;DR: The contribution of non-ideality to the total thermodynamic activity of hemoglobin in salt solution is shown to increase rapidly with increasing protein concentration and the results obtained do not preclude the presence of specific short-range attractive interactions between hemoglobin molecules.
TL;DR: Ten mutations are described that transform genotypic hermaphrodites of the nematode Caenorhabditis elegans into phenotypic males, but XO males (true males) are unaffected by these mutations; it is suggested that these genes are actually involved in hernaphrodite development and have no role in male development.
Abstract: Ten mutations are described that transform genotypic hermaphrodites of the nematode Caenorhabditis elegans into phenotypic males. These fall into three autosomal complementation groups, termed tra-1, tra-2 , and tra-3. Two alleles of tra-1 produce almost complete transformation, to a fertile male phenotype; such transformed animals are useful for analyzing sex-linked genes. All alleles of tra-1 and tra-2 are recessive; the one known allele of tra-3 is both recessive and maternal in effect. Where tested, both XX and XXX hermaphrodites are transformed into males, but XO males (true males) are unaffected by these mutations. It is suggested that these genes are actually involved in hermaphrodite development and have no role in male development.
TL;DR: The principal conclusion is that Fibonacci phyllotaxis follows as a mathematical necessity from the combination of an expanding apex and a suitable spacing mechanism for positioning new leaves.
Abstract: The principal conclusion is that Fibonacci phyllotaxis follows as a mathematical necessity from the combination of an expanding apex and a suitable spacing mechanism for positioning new leaves. I have considered an inhibitory spacing mechanism at some length, as it is a plausible candidate. However, the same treatment would apply equally well to depletion of, or competition for, a compound by developing leaves, and could no doubt accommodate other ingredients. The mathematical principles involved are clear when it is assumed that only two leaves (the contacts) position a new leaf. There is some experimental evidence for this assumption. Nonetheless, it is not a precondition for Fibonacci phyllotaxis, since a computer model shows that this pattern is generated even when many leaves contribute to inhibition at a given point. Indeed, the Fibonacci pattern seems to be a robust and stable mathematical phenomenon, a finding which goes some way to explaining its widespread occurrence throughout the plant kingdom.
TL;DR: The results indicate that the major mechanism for the decrease in CSP after transformation is reduction in its biosynthesis, although increased degradation and loss from the cell surface also contribute significantly.
TL;DR: The structure of two-dimensional crystals of cytochrome oxidase (Vanderkooi et al. , 1972) has been investigated and pairs of molecules are related by a crystallographic 2-fold axis perpendicular to the plane of the membrane, suggesting the possible occurrence of dimers in the natural state.
TL;DR: Results demonstrate the existence of two initiation sites, S 1 and S 2, for transcription of the galactose operon of E. coli and suggest that when CRP or cAMP is absent, transcription starts from S 2 in vivo.
TL;DR: This study illustrates the possibilities for genetic dissection of the development of a small set of nerves in a simple organism with chemotactic mutants obtained as worms swimming away from attractant or found amongst male potency mutants or mutants exhibiting erratic behavior.
Abstract: Eight of nineteen chemotactic mutants of the nematode Caenorhabditis elegans have morphological defects in the sensory endings of neurons at the tip of the head. The mutants were obtained as worms swimming away from attractant or found amongst male potency mutants or mutants exhibiting erratic behavior. The nineteen mutants fall into at least twelve complementation groups. Mutants E1034 and E1035, alleles of che-1, show morphological alterations in the sensory endings of amphidial neurons and inner labial type 2 neurons, both prospective chemosensory neurons. Both mutants contain noncomplementing ts sterile mutations linked to the chemosensory mutation. E1066 shows abnormalities in all the sheath cells associated with the sensory neurons and in the bundling pattern of the amphidial neurons. El 126 is structurally abnormal only in the sensory endings of inner labial type 2 neurons, supporting a chemosensory role for these neurons. E1033 (cke-2) and El 124 (cke-3) cause defects in the ciliary structure of all but one type of ciliated sensory neuron in the head. E1062 is grossly defective in head structure and the structure of the male copulatory organ, suggesting these opposite ends of the nematode rich in sensory structures share gene functions in embryogenesis. Our study illustrates the possibilities for genetic dissection of the development of a small set of nerves in a simple organism.
TL;DR: A simple and contained procedure for the rapid assay of the presence and size of plasmids similar to Col El is described.
Abstract: A simple and contained procedure for the rapid assay of the presence and size of plasmids similar to Col El is described. Bacteria are picked from an agar plate with a toothpick, lysed with dodecyl sulfate and heat, and placed directly on an agarose gel for electrophoresis.
TL;DR: Gynandromorph and clonal analyses suggest that the phenotype does not result from massive cell death followed by regeneration and/or duplication, but conjecture that the mutant phenotype is caused by a specific failure in the process of compartmentalization.
TL;DR: It appears that essentially all elements of the native conformation are attained simultaneously in the final stage of folding, within an unstable and flexible, yet relatively compact, form of the entire polypeptide chain produced by weak interactions between groups distant in the primary structure.