Main Cleavage Research Articles

Studies on the enzymic degradation of luteinizing hormone releasing hormone by rat pituitary plasma membranes

Degradation of luteinizing hormone releasing hormone (LH-RH) by purified plasma membranes from rat pituitaries was investigated. Synthetic LH-RH (0.5 mg/ml) was incubated (20 min, 37°C) with pituitary plasma membranes (750 μg protein/ml). The reaction was stopped by centrifugation at 4°C. The degradation products were isolated by high pressure liquid chromatography using a reversed-phase column. Amino acid analysis of the degradation products indicated that the N-terminal tripeptide (pGlu-His-Trp) and the N-terminal hexapeptide (pGlu-His-Trp-Ser-Tyr-Gly) sequence of LH-RH are the main degradation products. These results suggest that the main cleavage sites of LH-RH by the pituitary plasma membrane-bound enzymes are the Gly 6-Leu 7 and the Trp 3-Ser 4 bonds of the neurohormone.

Glyptograptus? persculptus (Salter), its tectonic deformation, and its stratigraphic significance for the Carys Mills Formation of N.E. Maine, U.S.A.

AbstractThe Carys Mills Formation of NE Maine represents the SW extension of the Matapedia Group and the White Head Formation of southern Gaspé, Quebec. This formation has yielded two main collections, one hitherto considered of Middle Ordovician age (zone 13 of Berry's 1960 Marathon, Texas, zonation) with 7 species referred to 4 genera, and one of the Early Silurian age. A revision of the supposed Middle Ordovician collections reveals that the graptolites are basal Silurian and consist of only one species, Glyptograptus? persculptus. Several hundred specimens, preserved both flattened and in three dimensions, the latter in iron pyrites, allow an analysis of both the rhabdosome changes wrought by diagenetic flattening and those caused by severe tectonic deformation. It is shown that those specimens lying parallel to the bedding plane lineation caused by a high‐angle main cleavage have a silhouette appearance close to Glyptograptus tamariscus (Nicholson), whilst those at right angles to this direction superficially resemble robust Amplexograptus spp., or Diplograptus s.s., or Diplograptus s.l. spp., thus explaining the stratigraphic assignment of earlier workers. An analogue video reshaper confirms the above conclusions.This determination assigns the whole Carys Mills Formation to the Lower Silurian, but the possibility that part of the formation is of Late Ordovician age cannot be excluded. This much is suggested by the Matapedia Group and the White Head Formation which are of Late Ordovician to Early Silurian age, and the Honorat Group, which has yielded graptolites of late Middle Ordovician age.

Picosecond pulse radiolysis and laser flash photolysis studies on polymer degradation of polystyrene and poly-α-methylstyrene

Recently early events in photolysis of polystyrene (PSt) solutions in chloroform and in 1,4-dioxane have been made clear by using a nanosecond laser flash photolysis system (Nd-YAG: 265 nm) at Hahn-Meitner-Institut [1]. Early events in radiolysis of PSt solution have also been studied by using a picosecond pulse radiolysis system at Univ. of Tokyo [2]. In the present paper, the difference and the similarity between photolysis and radiolysis of PSt and poly-α-methylstyrene (P-α-MeSt) are discussed. Important results are as follows; 1. (1) In both cases of radiolysis and photolysis, strong absorptions of intramolecular excimer have been observed for PSt ( λmax = 530 nm) and P-α-MeSt ( λmax = 520 nm) solutions in dioxane and cyclohexane, in addition to the monomer and excimer fluorescence of these polymers. In these solutions, those polymers are hardly decomposed. 2. (2) In both radiolysis and photolysis, charge-transfer complexes (PSt +δ, Cl −δ or P-α-MeSt +δ, Cl −δ) have been observed for PSt and P-α-MeSt solutions in chloroform (CHCl 3) and in carbon tetrachloride (CCl 4). In these solutions, polymers are effectively decomposed. The charge-transfer complexes are precursors of macroradicals. 3. (3) The charge-transfer complexes are mainly produced from ion pairs (PST +…Cl − or P-α-MeSt +…Cl −) in the case of radiolysis and from exciplexes of excited polymer molecules with solvent molecules in the case of photolysis. 4. (4) Since the presence of oxygen is prerequisite to main chain cleavage of PSt in CHCl 3 and in CCl 4, it is important to note that oxygen is not involved in initial stages of the main process of macroradical formation.

Theoretical aspects of the radiation effects of polymers

AbstractThe Millar–Wall–Charlesby empirical rule of radiation effects on polymers was theoretically examined. The theoretically calculated adiabatic potential curves of the main chain scission and side chain cleavage revealed that the effects of radiation on polymers are clearly interpreted as chemical reactions in the excited states; namely, that degradation occurs when little or no activation energy is required in the main chain cleavage reaction in the excited states, or, in other words, stabilization of the excited polymer molecule leads to the main chain cleavage. Crosslinking occurs when moderate or large activation energy is required in the main chain cleavage reaction in any electronic state and little or no activation energy is needed in the CH bond cleavage reaction in the excited states. Therefore stabilization of the excited polymer molecule leads to the formation of a polymer radical that crosslinks. It was concluded that Millar–Wall–Charlesby's rule is exact only when the shape of the adiabatic potential curve in the ground state reflects those in the excited states.

The correction of stratigraphic sections for tectonic finite strain in the Bygdin area, Norway

The deformed sediments beneath the Jotun Nappe were folded and then shortened vertically to produce the main cleavage. All the measurements from the Bygdin Conglomerate ( Hossack 1968a ) have been recalculated using harmonic means ( Lisle 1977 ) to get a better estimate of the conglomerate strain. The symmetry of this strain varies locally, but the regional strain can be estimated by integrating the extensions along finite strain trajectories. The minimum value of the integrated conglomerate strain consisted of 65 per cent vertical shortening, a transverse NW elongation of 160 per cent, and a NE elongation of 11 per cent along the Caledonian strike. The vertical shortening is the most constant strain, whereas the NW elongation varies between 390 per cent and 115 per cent. The early folding is estimated to have consisted of 26 per cent shortening along the bedding with 35 per cent extension normal to the bedding. The folding and the integrated strains have been combined in the simplest manner and it is estimated that the present stratigraphic thicknesses have to be multiplied by 2.15 to calculate their original thicknesses. The positions of the nappes before thrusting have also been estimated using the folding and the integrated strains. The Jotun Nappe has a minimum displacement of 290 km and the lower nappes have been thrust for distance between 100 km and 270 km.

On the kinetics of polymer degradation in solution—VII. Laser flash photolysis of poly-α-methylstyrene in solution

Poly-α-methylstyrene (PαMS) was degraded in CHCl 3 and CCl 4 solution by flash photolysis ( λ = 265 nm). The degradation, as detected by light scattering measurements, is caused by the attack on PαMS by solvent radicals, assumed to be formed mainly by energy transfer processes. The direct effect did not lead to detectable main chain cleavage as evidenced by experiments with PαMS dissolved in dioxane or methylene chloride. The time dependence of the decrease of the light scattering intensity (LSI) after the flash was measured. The observed first order lifetime τ(LSI) corresponds to the lifetime of lateral macroradicals P′ that decompose by main chain cleavage ( k = 3.5 × 10 2 sec −1). Molecular oxygen reacts with the lateral macroradicals with k = (5.5 ± 0.5) 10 5 M −1 sec −1. Only a minor portion of the product of this reaction (PO 2′) decays by main chain scission. Thus O 2 inhibits main chain scission significantly. By addition of cyclohexane and ethyl mercaptan, the main chain cleavage is inhibited. τ(LSI) was not affected by these compounds in the concentration range investigated ([C 6H 12]: up to 8.4 M; [C 2H 5SH]: up to 3 × 10 −3 M), indicating that they reacted with solvent radicals which otherwise attack the polymer forming lateral macroradicals.

Anisotropy of track registration in natural feldspar crystals

Abstract Terrestrial feldspars (orthoclase, anorthite, bytownite, labradorite, oligoclase, and albite) have been irradiated with 252Cf-fission products as well as Kr and Xe ions of different energies in order to study track length and track diameter as a function of crystal orientation. Both track length and track diameter of heavy particle tracks in orthoclase depend on the angle of incidence as well as on the angle of azimuth with respect to a fixed direction in the crystal surface plane. As to the plagioclase feldspars, only the track diameters appear to vary with crystal orientation. The different bulk and track etch rates for the main cleavage planes {001} and {010} are given. Within the plagioclase group the track registration properties were found to vary distinctly with the Ca content. Possible explanations for this observation are discussed.

Demonstration of β-lipotropin activating enzyme in porcine pituitary

Porcine β-lipotropin was incubated with a crude porcine pituitary homogenate, and the main cleavage products of the hormone were isolated and identified. Our results gave evidence for the enzymic cleavage of the Lys 46-Met 47, Arg 60-Tyr 61, Leu 77-Phe 78, and Lys 79-Asn 80 bonds of the β-lipotropin structure. The cleavage of the Arg 60-Tyr 61 peptide bond was accompanied with the concomitant release of opiate activity in the first period of incubation, provided that bacitracin was present in the incubation mixture. The enzyme was differentiated from trypsin or plasmin and appears to be a specific intracellular protease involved in the biosynthesis of pituitary endorphins.

Stratigraphy, structure and geochronology of ore leads in the Matsitama Schist belt of Northern Botswana

The Matsitama schist belt in northeastern Botswana comprises an area of metasediments, notably quartzites, limestones, shales and amphibolites that are bounded by granites and gneisses. The belt lies southwest of the Rhodesian cration and north of the Limpopo mobile belt. Stratigraphic, structural and lead isotopic evidence indicates that the Matsitama metasediments are equivalent to the Shashi metasediments in the Limpopo belt. There is strong evidence that the Matsitama and Shashi metasediments stratigraphically underlie volcanic rocks of the Tati belt which have been correlated with Archaean schist belts of about 2700 Ma of Rhodesia. Therefore, the Matsitama and Shashi rocks are at least as old as the schist belts of the Rhodesian craton and may represent a shallow-water facies that occurs only in the Limpopo area. There is no structural evidence that the Matsitama and Shashi metasediments were deposited unconformably on basement rocks, although the presence of gneiss, amphibolite and ironstone pebbles in a Matsitama conglomerate, as well as the presence of orthoquartzites, shows the existence of a basement source region. However, the surrounding granites intrude the Matsitama and Shashi metasediments and all underwent several deformation phases. The structural history of the Matsitama rocks can be described in terms of five phases of deformation. The main cleavage-producing deformation phase, F 2, folded the rocks into a major synform and intensely deformed them. Before this, however, the rocks had been folded and thrust so that part of the succession shows downward-facing F 2 structures and there are possibly repetitions of the stratigraphy due to imbrication. Structures of the F 3 and F 4 phases fold the main cleavage but locally are sufficiently intense to modify the shape of the finite strain ellipsoid. There is a major ductile shear zone of F 4 age, south of which F 4 folds are tight, while to the north, F 4 deformation is negligible. All of these structures can be correlated with deformation phases in the Tati schist belt to the east and in the northern part of the Limpopo mobile belt. Lead isotope evidence suggests that mineralization in the Matsitama metasediments occurred at least 2200 Ma ago, and that leads from Dihudi/Thakadu and Messina, in the centre of the Limpopo belt, underwent a two-stage history of events at 2600–2700 Ma and 2000–2100 Ma ago, agreeing with other geochronological evidence. The leads from Matsitama and Messina are isotopically distinct from leads from the Rhodesian schist belts, which show evidence of transfer to the crust some 3500 Ma ago. The absence of this 3500 Ma-old lead from the Matsitama and Messina environments may indicate different crustal conditions and possibly the absence of the Rhodesian-type early basement.

Plastic strain of particles of titanium carbide and zirconium carbide powders subjected to vibratory milling

Judged by the character of their elastic strain, zirconium and titanium carbides may be regarded as elastically isotropic materials. Under conditions of vibratory milling the main cleavage planes in these carbides are the planes {110}. Carbides of nonstoichiometric compositions are more brittle. The changes in strain behavior exhibited by the carbides in their homogeneity ranges are determined by the combined operation of the structural and electronic factors. In the Group IV carbides these two factors have opposed effects, but in Group V carbides they operate in the same direction. Arranged in order of increasing brittleness, on the basis of microplasticity as measured by rms strain, stoichiometric carbides form the series NbC < ZrC < TiC.

Cleavage of Si-C bond in silanes under influence of compounds of the 3d-transition metals

Compounds of the 3d-transition metals cleave the Si-Ph bond in Me3SiPh. The main cleavage products of the silane in alcohol are benzene, phenol, hexamethyldisiloxane, and trimethylethoxysilane. In their activity in cleaving the Si-Ph bond the halides of the 3d-transition metals fall into the sequence: FeCl3>TiCl3>CuCl2>VCl3>CrCl3>NiCl2>CoCl2>MnCl2 ≈FeCl2.

The geology of Howth and Ireland's Eye, Co. Dublin

AbstractThe Cambrian sediments in Howth and Ireland's Eye to the northeast of Dublin have been mapped and the submarine deltaic Censure Group and the overlying Nose of Howth Group, which consists of interbedded turbidites and olistostromes, have been distinguished. Large scale sedimentary disruption has accompanied detachment of quartzitic sandstone beds in the Censure Group, where the bases of detached blocks have slump features while their tops generally do not. This contrasts with the chaotic sedimentary breccias in the olistostromes of the Nose of Howth Group. Blocks in the Censure and Nose of Howth Groups are up to 450 m and 700 m across respectively. The turbidies have come from the southeast and east whereas the slumping appears to have been generated from the southwest.Slumping during sedimentation was followed closely by large‐scale folding and sliding of sedimentary or tectono‐sedimentary origin, and the bulk appearance of the sediments is due to these sedimentary and tectono‐sedimentary mechanisms. The main structure is an easterly facing, steep plunging syncline which locally is associated with a poorly preserved cleavage. This structure predated the main penetrative cleavage which is not axial planar to it.

Chemical-ionization mass spectrometry of beta-lactam antibiotics.

Chemical-ionization (CI) mass spectra are described for methyl esters of eight clinically significant penicillins and their breakdown products. The substances give spectra with very few fragment ions and contain easily discernible protonated molecule ions. The main cleavage reaction is postulated to involve a retro 2+2 Diels-Alder-type fragmentation of the beta-lactam ring liberating one fragment (m/e=174) that is characteristic of the penicillin nucleus and a second fragment that is molecule specific, as it contains the elements of the side chain. The other fragment ions, though interesting, are of minor intensity. The free acids, on the other hand, fragment more extensively because of their relative instability and lack of volatility. These spectra resemble electron impact spectra more closely and, though they encode more structural information, are less reproducible from run to run. The ease with which the esters can be made and the relative simplicity of their CI mass spectra make this method significant for the identification and characterization of beta-lactam antibiotics.

Mass spectrometry of heterocyclic compounds. V—Substituent effects on the fragmentation pathways of 3,5‐diphenyl‐1,2,4‐oxadiazole derivatives

AbstractThe 70 eV mass spectra of a number of derivatives of 3,5‐diphenul‐1,2,4‐oxadiazole substituted either in the 5‐phenyl (fifteen) or in the 3‐phenyl (four) position, have been studied using exact mass measurements and metastable determinations by the defocusing technique. The substituent effects on the heterocyclic cleavage are not very important for electron‐withdrawing and weak electron‐donating groups. The main cleavage is the formal retro 1,3‐dipolar cycloaddition with the positive charge retained by the C7H5NO (orYC7H4NO in the case of the 3‐substituted derivatives) fragment specifically containing the 3‐phenyl, as oreviously observed for 3,5‐diphenyl‐1,2,4‐oxadiazole using labelling experiments. Two other minor primary processes leading to benzoyl and nitrile ions, both containing the 5‐phenyl, become important in the case of the electron‐donating substituted compounds. Correlation of the abundance of these fragmednts and of the molecular ions with σ+ (para) Brown constants is discussed. Proximity effets are shown by some ortho derivatives.

North-South Trending Pre-cleavage Folds in the Skiddaw Slate Group of the English Lake District

THE polyphase nature of the deformation in the principal Skiddaw Slate tract was originally described by Simpson1. He considered that the main slaty cleavage and the folds to which it is axial planar are a result of the first deformation to which the slates were subjected. The trend of these structures varies from north-east-south-west to east-west due to later refolding, but can generally be considered Caledonoid. The existence of early north-south trending structures has also been advocated2–5. Helm and Roberts6 recently suggested that the Skiddaw Slates were deformed by a major north-south trending anticline and subjected to considerable erosion before the deposition of the Borrowdale Volcanic rocks. The evidence for early north-south trending folds has, however, been very limited and often of questionable validity. Recent work on the psammitic rocks near Buttermere now provides ample evidence to substantiate them and suggests that they may be present throughout the Skiddaw Slate Group.

Age of cleavage in the Skiddaw Slates in relation to the Skiddaw aureole

SummaryA recent hypothesis concerning the age of orogenic deformation of the Skiddaw Slates in the English Lake District has proposed that the main slaty cleavage (S1) and superimposed subhorizontal crenulation-cleavage (S2) are of intra-Ordovician age. A study of the fabric of the aureole of the (end-Silurian) Skiddaw granite shows that the granite was emplaced towards the end of the D1 deformation phase, but before the formation of S2. These structures are therefore of broadly end-Silurian age, and evidence of an intra-Ordovician orogeny in this area is lacking.

Models of a Degrading Polymer Network

Regular, two- and three-dimensional networks of linear analogs to elastic polymeric chains were degraded randomly in an attempt to establish a relationship between the force produced by a constantly strained network and the number of chain scissions. This behavior is important for the quantitative interpretation of chemical stress relaxation data. The models showed that the initial modulus of the three-dimensional networks should vary as the number of crosslinkages (tetrafunctional) to the 4/3 power. The initial rate of decay of the relative force for random main chain cleavage was (in the limit of infinite network size) equal to twice the rate of decay of the relative number of chains between the crosslinkages. At high degrees of degradation (relative number of chains between crosslinkages equal to 1 / e) the models indicated that the relative force would approach zero in the limit of infinite network size. The behavior of the models showed that the force decay of a degrading network is considerably more rapid than had been generally thought.

Thermal degradation of polymers with phenylene units in the chain. III. Polyarylates

AbstractThe thermal decomposition of three aromatic polyesters was studied in vacuo. The degradation products were analyzed by mass spectroscopy, infrared spectroscopy, and elemental analysis. Breakdown mechanisms are proposed. Primary cleavage of the ester linkages appears to take place either between the carbonyl and the oxygen or between the oxygen and the ring, yielding carbon monoxide and carbon dioxide in varying ratios. Another major decomposition product is a sublimate which seems to consist mainly of the phenolic component of the polyester. A polyester with a 2,2‐propylene linkage showed, as expected, early loss of methane. A pendent pentyloxy chain in one of the polymers is removed almost completely below 350°C with formation of alkanes and alkenes. Lack of oxygen in the fragments indicates that the main cleavage must occur between the ether oxygen and the aliphatic chain or with in the aliphatic chain.

Studies on metabolism of thiamine in rats. I. Cleavage of thiamine molecule in vivo.

It was found that in the rat about 50% of orally administered thiamine was decomposed into 4-methyl-5β-hydroxyethylthiazole (HT) and pyrimidyl derivative. It was demonstrated that 2-methyl-4-amino-5-hydroxymethylpyrimidine (HMP) was formed from thiamine as one of pyrimidyl derivatives. However, the amount of excreted HMP was extremely small as compared to that of excreted HT. It was concluded that the main cleavage of thiamine was not a direct hydrolysis into HT and HMP.

V.—The Explosion-breccia Pipes near Kentallen, Scotland, and their geological setting

SynopsisMore than twenty igneous intrusions, of widely varying composition and mainly in explosion-breccia pipes, cut the Appin Quartzite, Appin Limestone, Appin Phyllites and Cuil Bay Slates of the Dalradian Series which show evidence of a long and complex structural history. Early phases of tectonics and metamorphism (garnet-amphibolite facies) were followed by the dominant deformation of the region, referred to as main phase. The major structure of the Cuil Bay Synform, together with a series of parasitic folds, were developed during this phase together with a strong, retrogressive, regional cleavage. Late phase deformation acting prior to the development of the pipes produced steeply plunging open folds and box folds, of brittle type. The superimposition of these structures on main phase parasitic antiforms, in banded sequences of competent and incompetent units, produced dome-shaped structures with pipe-shaped zones of intensely fractured and brecciated rock. Late phase deformation after igneous intrusion was associated with the Great Glen Fault. The structural elements which exercised the dominant controls on the location and form of the pipes were the main phase regional cleavage, the main phase parasitic antiforms, the late phase steeply plunging open folds and the axial planes of the late phase box folds and open folds.A generalized sequence of events for a number of the pipes is: (1) explosive activity with shattering and brecciation, (2) emplacement of variable but generally hornblende-rich igneous types, representing crystallization at high to moderate gas pressure, (3) the emplacement of augite diorites or kentallenites representing crystallization at low gas pressure and (4) the emplacement of generally small bodies of leucodiorite–granodiorite, possibly representing secondary hybrid liquids. The other pipes show one or more of these events and the sequence is that expected in volcanic activity associated with the build up and release of pressure on the breaching of structural traps (formed by the Appin Quartzite). Explosive activity took place on the sudden release of gas when the gas-charged basic magma moved into the dome-shaped interference structures with their pipe-shaped zones of much fractured and brecciated rock.