Delta Sites Research Articles

The Names of the Tana Delta Sites

The Names of the Tana Delta Sites

Conformational flexibility in enkephalins: Solvent dependent transitions in peptides with Gly-Gly segments detected by circular dichroism

The widespread interest in developing structure-activity correlations for opioid peptides [1-3] has led to a large number of investigations on the preferred solution conformations of enkephalins [4-11]. The results of these studies have led to proposals ranging from \beta-turn conformations. With ${Gly}^2-{Gly}^3$ [14] or ${Gly}^3-{Phe}^4$ [4-10] as the corner residues. Evidence for the lack of preferred conformations in solutions, resulting from dynamic averaging between an ensemble of structures, has also been presented [11]. While a consensus has yet to be reached on the solution conformations of enkephalins, there is general agreement that receptor interactions presumably involve a folded, defined conformation of the penta-peptide [12-14]. The recognition of multiple receptor sites for opioid ligands [15-17], has provided a further impetus for studies of conformational flexibility in enkephalins, with the possibility that interaction at \mu and \delta sites may be mediated through different conformations of the peptides [18]. Here, we describe an unusual solvent-dependent conformational transition, in the protected fragment $Boc-Gly-Gly-Phe-Met.{NH}_2$ and ${Met}_5$-enkephalinamide which is abolished on restricting conformational freedom by substitution of Gly by \alpha-aminoisobutyryl (Aib) residues [19,20].

Linkage of an acetylenic secosteroid suicide substrate to the active site of delta 5-3-ketosteroid isomerase. Isolation and characterization of a tetrapeptide.

Linkage of an acetylenic secosteroid suicide substrate to the active site of delta 5-3-ketosteroid isomerase. Isolation and characterization of a tetrapeptide.

The actions of naloxazone on the binding and analgesic properties of morphiceptin (NH 2 Tyr-Pro-Phe-Pro-CONH 2), a selective mu-receptor ligand

Active in both binding and biological assays, morphiceptin (NH 2 Tyr-Pro-Phe-Pro-CONH 2), a potent opioid peptide derivative of β-casamorphine, binds specifically and selectively to mu or morphine-type receptors with little affinity for delta sites. Displacement studies of a variety of 3H-labeled opiates and enkephalins show biphasic curves. Naloxazone, which blocks irreversibly and selectively high affinity opiate and enkephalin binding, abolishes morphiceptin's inhibition of binding at low concentrations, suggesting that the high affinity binding of enkephalins and opiates represents a mu or morphine-type receptor. Unlike the reversible antagonist naloxone, naloxazone treatment in vivo inhibits for over 24 hours the analgesic activity of morphiceptin like it inhibits morphine, β-endorphin and enkephalin analgesia. Together, these studies imply that opiates and enkephalins bind with highest affinity to a mu receptor which mediates their analgesic activity. The 3H-D-ala 2-D-leu 5-enkephalin binding remaining after naloxazone treatment, representing a lower affinity site (K D 4 nM), is quite insensitive to morphiceptin inhibition and has the characteristics of a delta receptor. However, the 3H-dihydromorphine binding present after naloxazone treatment, which also represents a lower affinity site (K D 6 nM), is far more sensitive to both morphine and morphiceptin and may represent a second morphine-like, or mu, receptor.

The Namazga Civilization: An Overview

It became apparent during two exchange visits to the Soviet Union in 1978 and 19791 that the only major English summaries of the Aeneolithic and Bronze Age remains from Central Asia2 were dated and did not include adequate descriptions of major discoveries, such as the Murghab Delta sites. An immediate solution to this problem suggested itself: a collection of translated articles which both presented the latest discoveries in the area and illustrated current techniques and methods of analysis used by Soviet archeologists. In December 1978 I discussed the idea of such a publication with V. M. Masson, Director of the Central Asia and Caucasus Section of the Leningrad Branch of the Institute of Archeology, USSR Academy of Sciences, who agreed that such a publication was needed. He kindly provided me with a list of articles that he considered representative of current work in southern Central Asia.3 Although several articles were commissioned especially for this volume and every attempt was made to present th...

Initial perspectives on prehistoric subsistence in the Inland Niger Delta (Mali)

Abstract Information is presented about changes in subsistence resources and utilization from the beginning of permanent occupation to the present in the Inland Niger Delta of West Africa, a region long believed to be a centre of plant domestication. Excavations in 1977 at the western Delta site of Jenne‐jeno provided the first direct archaeological evidence of African rice and of the establishment of the remarkably stable Inland Delta subsistence complex: rice, fish and cattle. This complex sustained permanent occupation of large settlements in the floodplain far earlier than previously believed; Jenne‐jeno may have been larger than 10 hectares by 200 A.D. Excavation and extensive regional survey data suggest that the use of millets and sorghums is a recent introduction from outside the Delta. These conclusions support the view that the significant regional differences in the chronology of cereal cultivation must be appreciated before generalizations are made about the spread of food production within th...

Litter Size and Nursery Sites of the Hoary Bat Near Delta, Manitoba

Litter Size and Nursery Sites of the Hoary Bat Near Delta, Manitoba

Affinity labeling of the active sites of delta 5 -ketosteroid isomerase using photoexcited natural ligands.

Affinity labeling of the active sites of delta 5 -ketosteroid isomerase using photoexcited natural ligands.

Opening of the Gulf of Guinea and Geological History of the Benue Depression and Niger Delta

THE predrift fit of South America into the Gulf of Guinea is well known1. We suggest that the distinctive right-angled bends of the South American and African coasts result from three Cretaceous rift systems meeting at the site of the present Niger delta (A in Fig. 1). In the nomenclature of McKenzie and Morgan2 the Niger delta site was occupied in Cretaceous times by an RRR triple junction. Two of the arms of this junction have continued to spread taking the continents to their present positions, but the third arm, the Benue trough, after spreading for about 30 million years, closed before the end of the Cretaceous.

Virgil and Wolfcamp Fluvial, Deltaic, and Inter-Deltaic Embayment Depositional Systems in North and West-Central Texas: ABSTRACT

Virgil and lower Wolfcamp sediments on the Eastern shelf were deposited within 3 depositional systems--Bowie fluvial system, Cisco delta system, and Lake Hubbard interdeltaic embayment system--which are the subjects of this report. Complementary shelf-edge bank, slope, and basin systems, to be discussed by William E. Galloway, complete the facies tract. Bowie fluvial facies compose tabular and belted sandstone bodies characterized by braided and coarse-grained meander-belt sequences and sedimentary structures. Fine-grained meander-belt facies generally becoming finer upward, lateral accretionary point bar deposits, and characteristic sedimentary structures commonly occur high in the Bowie fluvial system, indicating decreasing tectonic activity in source areas. Basal fluvial channel facies normally cut subjacent deltaic facies and may overlie rocks of previous depositional episodes. Cisco deltaic facies are composed of prograding, prodelta mudstones that become coarser upward, delta front, channel-mouth bar and distributary channel sandstones, and aggradational crevasse splay facies, delta-plain mudstones, and coal or organic-rich clays. Local sandstone bars of destructional origin may fringe the delta facies. Lake Hubbard interdeltaic embayment facies flank deltaic lobes and are composed of mudstone, thin extensive sheet sandstone, and thin impure detrital coal. Some sheet sandstones reflect strandplain accretion, but more commonly they are reworked delta-front sands. Deltas prograded rapidly westward across the slowly subsiding Eastern shelf. Sediments from the east supplied crevassing delta lobes until avulsion of over-extended systems occurred. Delta construction, accompanied by deposition of complementary facies within nearby interdelta embayments, restricted open-shelf limestone facies to areas downslope or in areas of abandoned deltas. Channels were cut deeply into subjacent facies as prograding deltas extended fluvial erosion and deposition far across older deltaic facies. Marine processes slowly modified abandoned, compacting, and subsiding deltas. Winnowed sediment was swept into interdeltaic embayment mudflats and strandplains. In the absence of local terrigenous sediment, shelf limestones transgressed upslope and along the coast to coale ce over marsh-stabilized deltaic and interdeltaic areas. All environments could occur simultaneously, shifting with distribution of delta sites to produce repetitive End_Page 151------------------------------ sequences of thin superposed depositional systems. Deposition of fluvial and deltaic facies was rapid; deposition of destructional and transgressive facies represents most of the time consumed by deposition. Depositional systems shifted westward through time as the eastern flank of the basin was filled. End_of_Article - Last_Page 152------------

Permafrost Depths, Lower Mackenzie Valley, Northwest Territories

Reports 1965-66 ground temperature records for seven new sites established in the lower Mackenzie valley, indicating permafrost thickness of about 350 ft for Arctic Red River, 400 ft in site 14 mi west of Fort McPherson, 350 ft or more in the south central Mackenzie Delta, and 60-100 ft at four sites in the outer Delta which are within two feet of sea level. In the distal part of the Delta, where new islands are growing, perma- frost is aggrading downwards in the saturated alluvial soils.