Protein similarity measures

Secondary structural predictions about NPAs, and direct biophysical measurements, have demonstrated that the NPAs are rich in a-helix, with no p-structure either predicted from secondary structure prediction algorithms, or detected by circular dichroism (Kennedy et al, 1995b). In this they are the antithesis of the similarly sized cLBPs and lipocalins. The predictions are that each individual NPA unit protein will fold into four main regions of helix, and it has been speculated that the tertiary structure is as a four-bundle helix protein, similar to other invertebrate carrier proteins (Sheriff et al., 1987). 

Proteins are the major components by bulk in many biological samples and hence the weighing of a dried sample should give an estimate of the amount of protein present. Similarly, solutions that contain protein show values for specific gravity and surface tension which are in some way related to protein content. Measurements of the turbid ity resulting from the precipitation of protein and the absorption of radiation at specif ic wavelengths have all been used quantitatively... 

During a 30 minute incubation period, low levels of aldrin epoxidation (30-150 picomoles dieldrin/mg protein) were measured compared to those observed using enzyme sources such as aquatic Trichoptera Limnephilus sp. gut homogenates (1 pmole/mg protein 28) or rat liver homogenates (3000 pmoles/mg protein unpublished) under similar incubation conditions. Anisole metabolism based upon substrate disappearance was detectable but less than 5 picomoles/mg protein were transformed during the incubation period. Characteristics of the enzyme system are incompletely described owing to the low and variable levels of activity which have been obtained. 

Recently, studies were reported measuring the kinetics of stimulation of both cAMP and 3 using a mixing device and rapid quenching, in the millisecond range, in rat olfactory cilia (67). The response to a mixture of < orants peaks within 25 to 50 milliseconds, the time frame expected for receptors, with both cAMP and IP3. Similar measurements of the change in concentration of cAMP or IP3 were also done in the taste cell. Here mice, which were bred as bitter tasters and nontasters , were used as subjects. The bitter stimuli, sucrose octaacetate, strychnine and denatonium benzoate, were shown to increase IP3 levels in a membrane preparation from "taster" mice in the presence of GTP-protein and Ca but not in membranes from "nontaster" mice (68). 

We have seen that, purely using techniques of sequence comparison, the function of about 40% of genes sequenced from genome projects can be inferred from sequence identity or similarity measures or by motif comparison using a variety of techniques. It is known that proteins exhibiting insignificant sequence similarity often adopt similar tertiary structures, which themselves have similar (or at least re-... 

Speakman and Hirst (1933) and Speakman and Stott (1934) consider that an isoelectric region rather than an isoelectric point should be recognized similar results are observed with silk (Howitt, 1946). Lemin and Vickerstaff (1946) claim to have determined the isoionic point of wool by measurement of the pH at which addition of salt does not affect the pH. They obtained a value of 6.2 which is approximately the midpoint of the isoelectric region. It is not possible to determine the isoionic point of a protein by measurements made, as in the present instance, at constant salt concentration. The true value could be obtained by carrjdng out the... 

Similar measurements have been made by Arnold and Pak (1962) for the adsorption of proteins into films of other proteins. In some... 

For our THz transmission measurements, we used solutions of thioredoxin in distilled water obtained from Sigma. The sample preparation technique and experimental procedure has been described in Ref Samples of diluted water solutions with the concentrations between 0.1 mg/ml and 3 mg/ml of proteins were measured. Several samples were made from each solution. Samples are in the form of a cell assembled from two polycarbonate films and a spacer (12 pm thick) placed between them, with 10 pi solution inside the spacer. Each sample was measured several times and the resulting spectra were calculated against the background of similar cells made from pure deionized water between two PC films. 

Addition of PAA to an in vitro system for protein synthesis, in which [3H]-tryptophan or [3H]alanine incorporation into acid-precipitable hepatic proteins was measured, revealed that PAA competed similarly, but somewhat less, than did equimolar concentrations of unlabeled L-tryptophan or L-alanine.98 These findings suggested that PAA or a breakdown compound may become incorporated into proteins. 

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