Translocation, definition

Inhibition of Mineral Absorption in Excised Roots. More conclusive evidence that allelochemicals can inhibit mineral absorption has been obtained using purified allelochemicals and excised plant roots as the experimental system (Table 1). Use of excised roots eliminates the possibility that exists with intact plants that inhibition of translocation rather than absorption is responsible for decreased mineral content. Use of purified allelochemicals rather than plant debris or leachates allows more definitive conclusions to be reached regarding the capacity of allelochemicals to inhibit mineral absorption. 

In this chapter, it will be described how we have utilized endogenous and engineered Zn2+ binding sites to explore the structure and molecular function of Na+/Cl -depen-dent neurotransmitter transporters. The work has not only allowed the definition of the first structural constraints in the tertiary structure of this class of transporters, but also provided new insight into both conformational changes accompanying substrate translocation and mechanisms governing conformational isomerization in the translocation cycle. In the chapter, we will also review the theoretical and practical basis for... 

Transketolase 733,736 Translation of genetic information, 5. See also Protein synthesis definition of 5 nick 257 regulation of 536 Translocation... 

Definite structural requirements relating to activity (33, 34, 35, 55, 57, 58), translocation (56), and biodegradability (41) appear to exist for certain chemical groups of surfactants. Whether these also influence herbicide persistence in plants and roots requires further study. 

There are other advantages, too. With lower levels of insecticide, wildlife are not apt to be affected and environmental problems associated with pesticide use, e.g., groundwater contamination and pesticide translocation, will definitely be diminished or eliminated. 

The processes of prepropolypeptide synthesis, translocation, proteolytic processing and non-proteolytic modification can be enzymatically defined. These definitions are continuing to be developed and clarified. There are limited reports on insect neuropeptide processing (101.102. but these investigations should increase rapidly with the identification of precursor sequences via molecular genetics. The identification of processing enzymes, both proteolytic and non-proteolytic, will further open whole new areas for exploration. 

Conclusion. We have provided experimental evidence that the chaperonins meet the first criterion expected by their definition. They are molecules that, by their transient association with nascent, stress-destabilized or translocated proteins, prevent improper" aggregation. Chaperonins are not able to rescue aggregates once they are formed, nor do they appear to carry specific steric information, capable of directing a protein to assume a structure different from the one dictated by polypeptide primary sequence. 

The combined results of all the electron microscopic measurements alluded to in this section as well as results that had been reported by other laboratories present a model for the holoenzyme CFo F, embedded in a lipid bilayer, as shown in the lower portion of Fig. 6 (D). In this model, the a- and P-subunits in CFi are shown distributed in two overlapping layers, with the a-subunits closer to CFq. The smaller y-, 8- and e-subunits are asymmetrically distributed in the center surrounded by the a- and P-subunits. In the upper portion of Fig. 6 (D) is a top view of CFj drawn on the basis of signal-enhanced projections, such as those shown in Fig. 6 (B) and (C). The total length of CFq was found to be 8.3 nm. Although there was a lack of definitive information regarding subunits I, II and IV at the time, they were positioned above and below subunit III. The cylinder formed by the 8-kDa component of subunit III was considered to be the main pathway for proton translocation. The function of subunits I, II and IV in establishing a pathway for proton translocation or forbinding CF, was unclear at the time. ... 

The answer is a. (Murray, pp 812-828. Scriver, pp 3-45. Sack, pp 97-158. Wilson, pp 23—39.) Females have two alleles for each locus on the X chromosome because of their 46,XX karyotype. One normal allele is by definition sufficient for normal function in X-linked recessive disorders, so that females with one abnormal allele are carriers instead of affected individuals. Only when the companion normal allele is disrupted or missing does the abnormal allele cause disease. The Lyon hypothesis predicts that X inactivation is early, irreversible, and random, but some females inactivate only the X chromosome carrying the normal allele. X autosome translocations may disrupt an X chromosome locus and cause disease because the translocated autosome must remain active to avert embryonic death nonrandom inactivation of the normal X chromosome thus ablates expression of its normal allele. Females with Turner s syndrome, like males with 46,XY karyotypes, have only one X chromosome and can be affected with X-linked recessive diseases. Conversely, females with triple X or trisomy X syndrome have three alleles at each X chromosome locus and are not affected with X-linked recessive disorders. Since choices c, d, and e each require two genetic changes, they are less common than choice a. 

With cloned ricin genes available, the most definitive way of altering ricin B chain to make it suitable for inclusion in intact ricin ITs will be by genetic manipulation. In this way the B chain will be structurally modified so that it loses completely its ability to bind galactose but retains its ability to translocate A chain across a membrane. An important indication of the feasibility of this approach was the recent demonstration that these two functions of the B chain reside on separate domains in the molecule. Thus while chloramine-T-treated ricin B chains showed a dramatic reduction in their ability to bind galactose, their ability to potentiate the killing of cells treated with an A-chain IT was virtually unimpaired [112]. 

Modeling experiments allowed us to control for factors that might cause variation in field-based estimates of woody plant age-SOC relationships. Model estimates of SOC accumulation were comparable to field estimates for upland patch types and substantially lower than field estimates for lowland patch types (Table 4). Model estimates of soil N accumulation were substantially lower than field estimates, especially in lowlands. Given that woody patch age explained only 26-68% of the variance in soil C and N content, our field estimates of accumulation rates cannot be taken as definitive. Model results underestimated field observations, especially for N. Reliability of model estimates of soil carbon could likely be improved with a better understanding of how turnover of the substantial root mass (Table 2) might differ among patch types. Model estimates of soil N are likely constrained by lack of information on inputs associated with N, fixation, atmospheric N deposition, translocation between uplands and lowlands, and root turnover. 

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