scholarly journals HIGH NEGATIVE INTERFERENCE AND RECOMBINATION IN BACTERIOPHAGE T5

Genetics ◽  
1980 ◽  
Vol 96 (1) ◽  
pp. 25-41
Author(s):  
Barbara North Beck
Keyword(s):  
Molecular Structure ◽  
Fine Structure ◽  
Mismatch Repair ◽  
Direct Consequence ◽  
Significant Part ◽  
Significant Source ◽  
Negative Interference ◽  
Progeny Phage ◽  
Recombinant Formation ◽  
Bacteriophage T5

ABSTRACT The process of close recombinant formation in bacteriophage T5 crosses has been studied by examining the structure of internal heterozygotes (HETs), the immediate products of recombination events. The T5 system was chosen because it permits the study of internal heterozygotes exclusively, thus avoiding the ambiguities inherent in previous studies with T4. The heterozygotes were obtained by the nonselective screening of progeny phage in a prematurely lysed sample from an eight-factor cross. The molecular structure of each HET was inferred from the strand genotypes displayed among its progeny. This investigation presents unequivocal evidence that both overlap and insertion HETs are intermediates in recombinant formation and that insertion HETs are a significant source of close double recombinants. There is evidence suggesting that mismatch repair of overlap HETs could be the source of close triple exchanges. Thus, a significant part, and perhaps all, of the high negative interference for close-marker recombination observed in this system is a direct consequence of the fine structure of the recombinational intermediates. These findings are compatible with recombination models proposed by others, in which a single branched intermediate can give rise to HETs of both the overlap and insertion types.

scholarly journals The thermoelastic properties of muscle and their molecular interpretation

1937 ◽  
Vol 124 (834) ◽  
pp. 29-56 ◽  
Keyword(s):  
Molecular Structure ◽  
Mechanical Properties ◽  
Fine Structure ◽  
Physical Properties ◽  
Mechanical Behaviour ◽  
Thermoelastic Properties ◽  
Molecular Interpretation

As is the case with all physical properties, the mechanical properties of an object may be referred ultimately to the arrangement of its atoms and the forces between them. It is therefore possible under certain con­ditions to draw conclusions about the fine structure of an object from its mechanical behaviour. The analysis of thermoelastic properties in particular has led, in a number of cases, to definite conclusions about molecular structure, and it has been the object of the work described here to apply the same method to the study of muscle.

The infrared spectrum and molecular structure of sulphur trioxide

1970 ◽  
Vol 314 (1518) ◽  
pp. 329-339 ◽  
Keyword(s):  
Molecular Structure ◽  
Fine Structure ◽  
Electron Diffraction ◽  
Infrared Spectrum ◽  
Molecular Vibration ◽  
Electron Diffraction Data ◽  
Vibration Frequencies ◽  
Coriolis Coupling ◽  
Coupling Coefficients ◽  
Sulphur Trioxide

The rotational fine structure of several parallel and perpendicular type bands of sulphur trioxide, an oblate symmetric top, has been partially resolved and analysed. A more convincing assignment of the molecular vibration frequencies has been made than that based upon earlier measurements of the infrared and Ram an spectra. Rotational constants and Coriolis coupling coefficients have been derived, and a more accurate value of the S ═ O bond length has been obtained (1.41 ± 0.01 Å) than that previously assumed on the basis of electron diffraction data. Some vibrational-rotational interactions which affect the appearance of certain bands have been explained.

scholarly journals Capsid expansion of bacteriophage T5 revealed by high resolution cryoelectron microscopy

2019 ◽  
Vol 116 (42) ◽  
pp. 21037-21046 ◽  
Author(s):  
Alexis Huet ◽  
Robert L. Duda ◽  
Pascale Boulanger ◽  
James F. Conway
Keyword(s):  
Molecular Structure ◽  
High Resolution ◽  
Major Capsid Protein ◽  
Cryoelectron Microscopy ◽  
Viral Dna ◽  
Thin Walled ◽  
Capsid Maturation ◽  
High Level ◽  
Bacteriophage T5 ◽  
Icosahedral Capsid

The large (90-nm) icosahedral capsid of bacteriophage T5 is composed of 775 copies of the major capsid protein (mcp) together with portal, protease, and decoration proteins. Its assembly is a regulated process that involves several intermediates, including a thick-walled round precursor prohead that expands as the viral DNA is packaged to yield a thin-walled and angular mature capsid. We investigated capsid maturation by comparing cryoelectron microscopy (cryo-EM) structures of the prohead, the empty expanded capsid both with and without decoration protein, and the virion capsid at a resolution of 3.8 Å for the latter. We detail the molecular structure of the mcp, its complex pattern of interactions, and their evolution during maturation. The bacteriophage T5 mcp is a variant of the canonical HK97-fold with a high level of plasticity that allows for the precise assembly of a giant macromolecule and the adaptability needed to interact with other proteins and the packaged DNA.

Fine Structure of Growing Cellulose Fibrils of Ochromonas malhamensis Pringsheim (syn. Poteriochromonas stipitata Scherffel)

1970 ◽  
Vol 25 (9) ◽  
pp. 1017-1020 ◽  
Author(s):  
Detlef Kramer
Keyword(s):  
Molecular Structure ◽  
Fine Structure ◽  
Electron Microscope ◽  
Native Cellulose ◽  
Cellulose Fibrils ◽  
Elementary Fibrils

The stalked tunicae of the chrysomonadine Ochromonas malhamensis consist of mirofibrils which in contrast to often described plant cellulose fibrils do not have the appearance of one-layer ribbons, but are composed of 10-20 Å thick elementary fibrils, that are very loosely fasciated. The reason for this uncommon structure is thought to be found in the function of the tunicae. Since the elementary fibrils of Ochromonas extend unilaterally, electron microscope studies could be made on the growing ends of the fibrils, several types of which could be discerned. The importance of these structures to the different theories of the growth and the molecular structure of native cellulose is discussed.

The Bakerian Lecture: Molecular structure in the polysaccharide group

1959 ◽  
Vol 252 (1270) ◽  
pp. 287-312 ◽  
Keyword(s):  
Molecular Structure ◽  
Fine Structure ◽  
Biological Function ◽  
Structural Features ◽  
Molecular Structures ◽  
Molecular Architecture ◽  
Considerable Time ◽  
General Acceptance ◽  
Naturally Occurring ◽  
Precise Knowledge

It has been clear for some considerable time that a more precise knowledge of the molecular structure of the polysaccharides is needed for the solution of many problems in biology and medicine. This was emphasized by Sir Norman Haworth in the Bakerian Lecture delivered in 1944, when he reviewed the position then reached concerning the structure, biological function and synthesis of typical polysaccharides. In this connexion it is of interest to recall that by 1944 the view that naturally occurring colloidal substances such as starch and cellulose possessed molecular structures held together by normal co-valent bonds had received general acceptance for less than 20 years. Furthermore, the evidence for the main structural features of the polysaccharides had been acquired by difficult and laborious experimental methods which normally involved the manipulation of large quantities of material. Some idea of the general molecular architecture of many polysaccharides had been gained, but the methods then available were not capable of delving much deeper into the detailed structural features. This fine structure is nevertheless of particular importance, since the presence of irregular features in the molecule, even in slight degree, may alter quite markedly the behaviour of these high polymers. It will be readily understood also that the fine structure of these macromolecules is a matter of great moment in enzymology.

Afrikaans circumpositions

2020 ◽  
pp. 1-44
Author(s):  
Erin Pretorius
Keyword(s):  
Fine Structure ◽  
Word Order ◽  
Direct Consequence ◽  
Structural Components ◽  
Prepositional Phrases ◽  
Structural Relation ◽  
Particle Verbs ◽  
Structural Positions

Abstract Circumpositions in Afrikaans present several puzzles: (i) they always encode spatial paths, but spatial paths can also be encoded by prepositional phrases; (ii) they can be doubling or non-doubling, and (iii) they exhibit disharmonic word order of the kind that appears to violate the Final-over-Final Condition (FOFC). In this paper, I argue that circumpositions offer support for the existence of a directional head [dir] in the fine structure of the Afrikaans verbal domain, and that this head is lexicalised by adpositional material in circumpositional expressions. I show that Afrikaans grammar distinguishes Route-paths from Goal-/Source-paths, and argue that whereas [dir] selects a [pathP] in the structure underlying Goal-/Source-paths (circumpositional expressions), Route-paths (prepositional expressions) are ‘bare’ [pathP] structures. I argue that since circumpositions identify structural components in different Spellout Domains, double-insertion of adposition-like material is required to exhaustively lexicalise the structure, and the disharmonic word order is understood as a direct consequence of the fact that [dir] is located in Afrikaans’ head-final verbal, which addresses the concern arising around FOFC. Finally, given that the adpositions in circumpositional expressions are shown to occupy structural positions that are distinct from that of de-adpositional V-particles, the paper also addresses the structural relation between circumpositions and particle verbs in which adposition-like material lexicalises a resultative [res] node in the verbal domain.

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