Host sequences

Fig. 3. Zr/Ti02 vs. Nb/Y in rocks of the Big Lake VMS host sequence. Note two distinct sample populations. Fields are from Pearce (1996) after Winchester Floyd (1977).

BLUC peridotite chemostratigraphy, downward-fining cumulate flows, and asymmetry of hydrothermal alteration suggest the local host sequence to the VMS is overturned ... 

The Brunswick Subduction Complex (BSC) is best know as the host sequence to world class, syngenetic volcanogenic massive sulfide deposits of the Bathurst Mining Camp (BMC) hosting deposits such as the giant Brunswick No. 12 VMS deposit (>300 Mt of massive sulfides). Less well known are the syntectonic, precious-metal breccia and (or) vein deposits/occurrences in the BSC. The shear zone-hosted Middle River gold deposit (MRG) is the most significant of these and has returned assays of up to 7.44 g/t Au over 6.5 m (DDH MR-05-06). 

The interpretation of lithogeochemical data from basaltic structural domes is complicated by lithological changes associated with the transition from basalt to overlying siliciclastic rocks, as well as by the polydeformed nature of the host sequence. Ferroan carbonate alteration is well developed, and low-level Au enrichment extends for a considerable distance away from zones of economic interest. Arsenic and Sb/AI anomalies are restricted to within approximately 10 m of mineralized zones. Sericite alteration is indicated by Na depletion and K enrichment in basalt within 20 to 40 m of mineralized zones. A number of other elements, including Mn, P, S, Zn, Mo, Cu, Se and Ba, are variably enriched within the rocks hosting Au mineralization, but it is not clear whether elevated concentrations of these elements are a product of syn-sedimentary exhalative activity or result from later hydrothermal alteration. 

The rift setting in which the host sequence was deposited. 

Integration of the dsDNA into the host DNA can occur at many places. The mechanism of integration probably resembles that used by phage A, (Fig. 27-27) and accounts for the duplication of host sequences at the two ends of the integrated virus. A virally encoded integrase catalyzes the process (see also Chapter 27, Section D,3).715 717 It is the integrated virus that is transcribed to form new (+) viral RNA strands. 

The response of the plant host to rhizobial LPS is an area that requires more investigation. The availability of numerous rhizobial symbiont genome sequences, defined LPS mutants and isolated structures from these mutants, as well as a number of legume host sequences (i.e. M. truncatula, Glcyine max, and Lotus japonicus) offer the tools required to define the structure-function aspects that rhizobial LPS play during symbiosis. 

Data for characterisation of faults in the subsurface are limited to two sources, seismics and wells. Seismic reflection data allow the displacement distribution over a fault surface to be mapped while well and core data may allow determination of fault rock types and deformation mechanisms at specific points, in addition to characterising the lithologies of the host sequence. It is evident from outcrop studies that the internal geometries of fault zones are usually complex, in terms of the numbers of individual slip surfaces, the partitioning of slip between them and in the distribution of different fault rocks, all of which vary over a fault surface. This 3-D complexity of fault zone structure may not be apparent from either seismic or core data but is nevertheless crucial to the bulk hydraulic properties of a fault. 

Leclercq I., Mortreux F., Cavrois M., Leroy A., Gessain A., Wain-Hobson S., Wattel E. (2000). Host sequences flanking the human T-cell leukemia virus type 1 provirus in vivo. J. Virol. 74 2305-2312. 

Toniolo and Mutter et al. adopted the host-guest idea to study the impact to the guest amino acids glycine and L-proline on the preferred conformation of various host sequences... 

Both Pro and Gly have to be considered unusual among the 20 naturally occurring a-amino acids. Their significant influence on the conformation of a host peptide could a priori be expected from a look at the conformational energy maps (Rama-chandran maps) of fiiese two residues. To make it possible to extoid the host-guest principle to amino acids with less dramatic conformational behavior, the original approach was modified such as to insert two vicinal guest residues into the host sequence. 

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