Structure of Chromatin

Physico-chemical experiments show that histones are not evenly distributed in chromatin. About half of the DNA is “open” and not covered with proteins.     

Structure of galtamycin

Structure of galtamycin, a novel anthracycline antibiotic was assessed with 1H NMR, 13C NMR and mass spectroscopy. Galtamycin includes an unusual aglycone i.e. galtamycinone containing the C-glycoside bond and glycosylated with trisaccharide consisting of two fragments of L-rodinose and one fragment of D-olivose.     

Structure of Xanthocidin

A burnt flavoring compound, which imparts to aged sake its characteristic and dominant flavor, was isolated by Diaion HP–20, silicic acid and Dowex 1–X8 (CH₃COO^?) column chromatography and chloroform extraction. Based on thin-layer and gas liquid chromatography, UV and GC–MS spectral data, it was identified as 3-hydroxy-4,5-dimethyl-2 (5H)-furanone and its structure was also confirmed by synthesis. It was suggested that this compound was formed by the condensation of a-ketobutyric acid with acetaldehyde which occurred from degradation of threonine.     

Structure of brevobiose

A new disaccharide, brevobiose (1), has been isolated from the dried twigs of Sarcostemma brevistigma. The structure of 1 has been established as 4-O-(6-deoxy-2-O-methyl-β-d-allopyranosyl)-d-boivinose on the basis of chemical and spectroscopic evidence, and identification of its hydrolysis products.     

Structure of porosin

The reported structure of porosin, 3a-allyl-5-methoxy-3-methyl-2-veratryl-2,3,3a,6,7,7a-hexahydro-6-oxo-benzofuran, is revised with respect to Δ-4,5. ¹H NMR (LIS), UV and photochemical evidence shows that the double bond is located at the 7,7a-position.     

Structure of Thermolysin

Results of the chemical and X-ray analyses are combined to locate the active site and the calcium binding sites.     

Structure of ivory

Profiles with all orientations have been used to visualize the 3D structure of ivory from tusks of elephant, mammoth, walrus, hippopotamus, pig (bush, boar, and warthog), sperm whale, killer whale, and narwhal. Polished, forming, fractured, aged, and stained surfaces were prepared for microscopy using epi-illumination. Tusks have a minor peripheral component, the cementum, a soft derivative of the enamel layer, and a main core of dentine=ivory. The dentine is composed of a matrix of particles 5-20 microm in diameter in a ground substance containing dentinal tubules about 5 microm in diameter with a center to center spacing of 10-20 microm. Dentinal tubules may be straight (most) or curly (pigs). The main findings relate to the way that dentinal tubules align in sheets to form microlaminae in the length of the tusk. Microlaminae are sheets of laterally aligned dentinal tubules. They are axial but may be radial (most), angled to the forming face (pigs and hippopotamus canines), or radial but helical (narwhals). Within the microlaminae the dentinal tubules may be radial, angled to the axis (whales, walrus, and pigs), or may change their orientation from one microlamina to the next in helicoids (canines of hippopotamuses, incisors of proboscidea). In the nonbanded, featureless ivories from the hippopotamus incisors, the dentinal tubules form radial microlamina from which the arrangements in other ivories can be derived. In the canines of hippopotamuses and incisors of proboscidea, the dentinal tubule orientation changes incrementally from one microlamina to the next in a helicoid, a stack of dentinal tubules that change their orientation by 180 degrees anticlockwise. Dentinal tubules having different orientations are laid down concurrently, not layer by layer as in most examples of helicoidal architecture (e.g., insect cuticle). In proboscidean ivory, the microlaminae are radial, normal to the banding of growth layers marking the plane of deposition. They form radial segments with each 180 degrees turn in the orientation of their constituent dentinal tubules. Below the cementum they are almost complete 180 degrees helicoids, but nearer to the core they become narrower with the loss of radially oriented dentinal tubules. These truncated helicoidal patterns appear in longitudinal profile as VVVV feather patterns rather than intersection intersection intersection intersection, each V or intersection being the side view of a partial or complete helicoid. The Schreger pattern in proboscidean ivory consists of these helicoids divided tangentially into columns in the length of the tusk. Narwhals have the most abundant matrix particles with their radial/helical dentinal tubules having a twist opposite to that in the cementum.     

Structure of caveolae

The introduction of the electron microscope to the study of the biological materials in the second half of the last century has dramatically expanded our view and understanding of the inner workings of cells by enabling the discovery and study of subcellular organelles. A population of flask-shaped or spherical invaginations of the plasma membrane were described and named plasmalemmal vesicles or caveolae. Until the discovery of caveolin-1 as their first molecular marker in early 1990s, the study of caveolae was the exclusive domain of electron microscopists that demonstrated caveolae at different surface densities in most mammalian cells with few exceptions. Electron microscopy techniques in combination with other approaches have also revealed the structural features of caveolae as well as some of their protein and lipid residents. This review summarizes the data on the structure and components of caveolae and their stomatal diaphragms.     

Structure of tigmobiose

A new, nonreducing disaccharide, tigmobiose, has been isolated from the dried twigs of Sarcostemma brevistigma. On the basis of chemical and spectroscopic evidence, and identification of its sole hydrolysis product, its structure has been established as 2,6-dideoxy-β-d-ribo-hexopyranosyl 2,6-dideoxy-β-d-ribo-hexopyranoside (β-d- digitoxopyranosyl β-d-digitoxopyranoside).     

Structure of orthenthose

A new tetrasaccharide, orthenthose, has been isolated from the dried twigs of Orthenthera viminea (Family: Asclepiadaceae). By spectral and chemical procedures, this new tetrasaccharide has been shown to be O-α-l-oleandropyranosyl-(1→4)-O-α-l-oleandropyranosyl-(1→4)-O-α-l-oleandropyranosyl-(1→4)-β-l-oleandropyrano se.     

Structure of chromosomes

The number of gyres, mode, and direction of coils, centromere, secondary constriction, and telomere were studied in the human somatic chromosomes in terms of spiral structure, employing the newly developed technique involving a hypotonic treatment. Results obtained are: 1. the number of gyres is most probably constant in analogous chromosome from different cells; 2. the direction of coils is random; 3. each ehromatid is accepted as a unit of chromonema coiling; 4. the centromere seems to be a regionally elongated portion of the chromonema, without showing any differentiated structure; 5. chromonemata at secondary constrictions usually appear as uncoiled or less tightly coiled entities, and 6. two different types of the telomere structure were observed, one being a pointed-end type, while the other is a rounded-end type (Summary see p. 424). Supported by a grant from the National Institute of General Medical Sciences, U.S.P.H.S. (GM 14185).