Identical Half Research Articles

Design and construction of planar mm-wave accelerating cavity structures

Feasibility studies on planar millimeter-wave cavity structures have been made. The structures could be used for linear accelerators, free-electron lasers, mm-wave amplifiers, or mm-wave undulators. The cavity structures are intended to be manufactured by using DXL (deep x-ray lithography) microfabrication technology. The frequency of operation can be about 30 GHz to 300 GHz. For most applications, a complete structure consists of two identical planar half structures put together face-to-face. Construction and properties of the constant gradient structures that have been investigated so far will be discussed. These cavity structures have been designed for 120 GHz 2π/3-mode operation.

The effects of symmetrical recombination site hixC on Hin recombinase function.

An artificial recombination site hixC composed of two identical half-sites that bind the Hin recombinase served as a better operator in vivo than the wild type site hixL (Hughes, K. T., Youderian, P., and Simon, M. I (1988) Genes & Dev. 2, 937-948). In vitro binding assays such as gel retardation assay and methylation protection assay demonstrated that Hin binds to hixC as tightly as it binds to hixL, even when the sites are located in negatively supercoiled plasmids. However, hixC served as a poor recombination site when it was subjected to the standard inversion assay in vitro. hixC showed a 16-fold slower inversion rate than the wild type. A series of biochemical assays designed to probe different stages of the Hin-mediated inversion reaction, demonstrated that Hin dimers bound to hixC have difficulty in forming paired hix site intermediates. KMnO4 and S1 nuclease assays detected an anomalous structure of the center of hixC only when the site was in negatively supercoiled plasmids. Mutational analysis in the central region of hixC and assays of paired hix site formation with topoisomers of the hixC substrate plasmid suggested that Hin is not able to pair hixC sites because of the presence of the anomalous structure in the center of the site. The structure does not behave like a DNA "cruciform" since Hin dimers still bind efficiently to the site. It is thought to consist of a short denatured "bubble" encompassing 2 base pairs. During the study of mutations in the center of hixC, it was found that Hin is not able to cleave DNA if a guanine residue is one of the two central nucleotides close to the cleavage site. Furthermore, Hin acts in a concerted fashion and cannot cleave any DNA strand if one of the four strands in the inversion intermediate is not cleavable.

DNA binding site preferences and transcriptional activation properties of the Arabidopsis transcription factor GBF1.

The G-box is a cis-acting element found within the promoters of many plant genes where it mediates expression in response to a variety of different stimuli. This palindromic DNA motif (CCACGTGG) is composed of two identical half sites, the base pairs of which we have numbered -4 to +4 (numbering from 5' to 3'). Both half sites are involved in the binding of the bZIP protein GBF1, a member of the GBF family of Arabidopsis thaliana. Here we demonstrate using the random binding site selection method that GBF1 interacts with, in addition to the palindromic G-box, other DNA motifs that fall into seven distinct groups. All groups share the ACGT core sequence, common to most DNA motifs bound by plant bZIP proteins so far characterized. Our studies demonstrate that a high affinity GBF1 binding site is further defined by the following two parameters: first, all sites contain a G residue at position +3 (as in ACGTG) and secondly, only certain base pair combinations are allowed at positions -4, -3 and +4. Two of the identified groups (TGACGTGG and TGACGTGT) contain the base pairs TG at positions -4 and -3 and hence resemble the binding sites of another class of plant bZIP proteins (TGACGT/C binding proteins). However, GBF1 only interacts with the TGACGT sequence if the two 3' distal nucleotides (positions +3 and +4) are occupied by GG or GT. These data define the differences between a G-box binding protein and TGACGT/C binding proteins. The N-terminal domain of GBF1 is defined by a high proline content. Such regions were also identified in proteins related to GBF1. We demonstrate that this N-terminal proline-rich domain of GBF1, when fused to a heterologous DNA binding domain, stimulates transcription in both plant protoplasts and mammalian cells. These extensive DNA binding studies and the characterization of the GBF1 activation domain will facilitate both the identification of regulatory elements and the in vivo function of GBF1.

Development and phenotypic variability of genetically identical half mouse embryos

The growth and development of three groups of genetically identical F1 C57BL/6J female x SJL/J male mice were compared to examine whether embryo manipulation affects subsequent postnatal growth and development of mammalian embryos: (1) controls--the natural offspring of timed matings, (2) transferred controls--offspring from 2-cell embryos transferred to recipients 1 day asynchronous, and (3) transferred half embryos--offspring developing from one blastomere from the 2-cell stage transferred to recipients 1 day asynchronous. The recipients were C57BL/6J females. No differences were found in the age at eye opening and vaginal opening. At 5 days after birth the median body weights of the controls were lower than the weights of the transferred groups. This result could be explained by the larger litter size in the control group. The overall variances of the body weights did not differ between the groups. By the second week after birth a marked increase in overall variances of body weights of the transferred groups, compared with the control group, was observed. At 5 days after birth, the median tail lengths did not differ between groups, and overall variances were the same. By the second week, the overall variances of the tail lengths of the transferred groups were significantly greater than that of the control group. Possibly the increased overall variances of the body weight and the tail length of the transferred groups are related to the smaller litter size in these groups which affects competition for food and the ambient temperature in the nest. The overall results suggest newborn mice that have developed from half embryos have compensated for their initial deficiency. The intraclass correlation coefficients for body weight and tail length are approximately the same in all groups. Thus, producing artificial identical twins by embryo bisection may not affect their potential usefulness in the design of experiments.

Phosphorylation of 19S thyroglobulin.

Thyroglobulin (TG), one of the largest known eukaryotic proteins (Mr 660.000, sedimentation coefficient 19S), plays a central role in thyroid hormonogenesis. TG presents several characteristics of special interest: (i) it represents the major biosynthetic product of thyroid follicular cell1; (ii) under denaturing conditions it can be dissociated into identical half molecules (Mr 330.000, sedimentation coefficient 12S)2; (iii) its native structure is essential for an efficient thyroid hormone production3. TG is synthesized on membrane bound polysomes4 and core-glyco-sylated in rough endoplasmic reticulum5. Along its migratory pathway TG passes through the Golgi apparatus in which carbohydrate processing is accomplished and terminal sugars are added6, it is then secreted into the follicular lumen, where iodination takes place7. The ultimate fate of thyroglobulin is the reabsorption by pinocitosis, proteolytic degradation in the lysosomes and release of thyroid hormones in the blood stream.

Udder infection of goats by coagulase-negative staphylococci

Infection of udder halves by coagulase-negative staphylococci in seven commercial goat herds was studied in conjunction with the California Mastitis Test (CMT). Nine different species were identified and only 10% of strains belonged to groups which could not be identified with any of the known Staphylococcus species. The most prevalent species were Staphylococcus epidermidis (47.7%) and Staphylococcus caprae (19.7%). About half od the coagulase-negative staphylococcal infections gave negative CMT scores. The score was independent of the species of staphylococci involved and the stage of lactation. About 60% of the coagulase-negative staphylococcal species isolated were reisolated in the identical half udder during the following lactation.

Cardiac deceleration and reflex blink facilitation.

ABSTRACTTheories differ in their predictions of how skeletal reflex activity should vary with cardiac deceleration, an index of orienting. Although Graham (1975) reported that reflex blinking was facilitated under uncertainty conditions eliciting cardiac deceleration, theoretical implications remained unclear. Graham hypothesized that facilitation was not due to orienting per se but to rebound when orienting was terminated by the blink‐eliciting stimulus. This hypothesis was tested in the present research by manipulation of attentional requirements. In Experiment 1, 24 undergraduates received identical stimulation but half made an attention‐focusing discrimination between durations of noise startle stimuli and thus maintained attention on the stimulus past the time of reflex initiation; half of the subjects discriminated durations of non‐startling tones and thus could terminate orienting when a noise stimulus occurred. In both groups, orienting was induced by a lead stimulus that was followed equally often by noise and tone. The hypothesis was disconfirmed. Blinks were equally facilitated in both groups compared to no‐lead stimulus control trials. A second experiment, designed to induce more persistent cardiac deceleration under maintained attention conditions, produced similar results.

On the size and chemical nature of the polypeptide chain of bovine liver rhodanese

Evidence from molecular weight studies and sequence analysis of bovine liver rhodanese indicates that the enzyme is a single polypeptide of molecular weight 35,200, and not a dimer of identical subunits half this size. The rhodanese molecule contains 317 amino acids including 5 methionines, 4 cysteines, and 5 tryptophans. As expected, six fragments were produced by cleavage with cyanogen bromide and these have been aligned in the enzyme with the aid of overlapping tryptic peptides isolated from a [ 14C] carboxymethylmethionyl rhodanese derivative. The cyanogen bromide fragments account for all of the amino acid residues of the parent rhodanese molecule. Methionine residues are located at positions 72, 112, 214, 217, and 235 in the polypeptide chain and the active site cysteine is at position 251, in the carboxyl-terminal segment of the molecule.

Nature of the ribosomal RNA transcribed from the X and Y chromosomes of Drosophila melanogaster

In Drosophila melanogaster there is one nucleolar organizer ( NO) on each X and Y chromosome. Experiments were carried out to compare the ribosomal RNAs derived from the two nucleolar organizers. 32PO 4-labelled ribosomal RNA was isolated from two strains of D. melanogaster, one containing only the X chromosome NO, the other containing only the Y chromosome NO. 28 S and 18 S RNA from the two strains were subjected to a variety of “fingerprinting” and sequencing procedures. Fingerprints of 28 S RNA were very different from those of 18 S RNA. Fingerprints of “X” and “Y” 28 S RNA were indistinguishable from each other, as also were fingerprints of “X” and “Y” 18 S RNA. In combined “T 1 plus pancreatic” RNAase fingerprints several distinctive products were characterized and quantitated. Identical products were obtained from X and Y RNA, and the molar yields of the products were indistinguishable. Together these findings imply that the rRNA sequences encoded by the X and Y NOs are closely similar and probably identical to each other. Two further findings were of interest in “T 1 plus pancreatic” RNAase fingerprints: (1) in 28 S (as well as in 18 S) fingerprints several distinctive products were recovered in approximately unimolar yields. This indicates that 28 S RNA does not consist of two identical half molecules, though it does consist of two non-identical half molecules together with a “5.8 S” fragment. (2) Several methylated components in Drosophila rRNA also occur in rRNA from HeLa cells and yeast. This suggests that certain features of rRNA structure involving methylated nucleotides may be highly conserved in eukaryotic evolution.

Properties and subunit structure of the B component of Pseudomonas putida tryptophan synthetase

The purified B component of Pseudomonas putida tryptophan synthetase has absorption maxima at 278, 332, and 415 nm in potassium phosphate buffer at pH 7.0. After borohydride reduction, with the cofactor covalently attached to the polypeptide chain, the protein loses the maxima at 332 and 415 nm, but acquires a new absorption band at 320 nm. The K m for the binding of pyridoxal-5′-phosphate to the enzyme was found to be 5 × 10 −7 m. One of the substrates in the indole to tryptophan reaction, l-serine, has a marked effect on the heat stability of the holoenzyme. The molecular weight determined by acrylamide gel electrophoresis and by ultracentrifugation is 86,000 ± 2,000. Upon treatment with detergent, performic acid, or urea, two identical subunits half the size of the native enzyme are found. Two alanine residues are released by carboxypeptidase A digestion of performic acid-oxidized B protein. No strong aggregates are formed between E. coli tryptophan synthetase A protein and P. putida B protein, and no hybrid B protein is detectable after dissociation of a mixture of E. coli and P. putida B proteins in urea and reaggregation in potassium phosphate buffer.

Axial compression of an elastic circular cylinder in contact with two identical elastic half spaces

This paper considers the axially-symmetric compression of an elastic circular cylinder of finite length in contact with two identical elastic half-spaces. Both the frictionless and the adhesive contact problems are solved. Continuity of the stress and displacement components at the interfaces leads to simultaneous integral equations from which the surface stresses are determined. Numerical solutions are obtained for various combinations of the elastic moduli of the media and for some values of the height-width ratio of the cylinder; the corresponding normal and shear stress distributions are plotted. Values of the relative approach of the half-spaces are presented which may be of interest in the interpretation of the results of the standard compression test. The well-known equations of the elastic half-space are used and a general stress function is developed for the cylinder from which a wide class of boundary-value problems may be solved by the methods presented.

A new hemoglobin variant with sickling properties.

THE red-cell sickling tendency of certain persons has long been a matter of great interest. Study of this problem by Pauling and his associates1 led to the suggestion of a genetic change in hemoglobin formation that resulted in synthesis of different globin fractions for normal and sickle-cell hemoglobin. Subsequent investigation by Ingram2 has shown the specific globin abnormality to be a single amino acid substitution, valine for glutamic acid, in each identical half hemoglobin molecule containing approximately 300 amino acids. Sickle-cell anemia thus became the first example of a molecular disease in which the product of gene mutation was characterized . . .