Protein mass ratio

A typical isotherm, for lysozyme, is shown in Fig. 1. There is a knee at 0.05—0.1 h (g of water per g of protein, mass ratio) and a strong upswing to the isotherm near 0.25 h. Sorption measurements on model polymers and chemically modified proteins (see Watt and D Arcy, 1976 ... 

Archaea exhibit intralineage variations of their ribosome type. To generalize, all archaea contain ribosomes (especially their small subunits) that are considerably richer in protein than those of bacteria, with the exception of the Halobacteriales and of methanogens belonging to the Methanomicrobiales and Methanobacteriales. These differ from other archaea in harbouring ribosomes having the same protein mass and the same (3 2) RNA to protein mass ratio as those of typical bacteria. Because the size and the secondary structure of the archaeal rRNAs do not differ from those of bacterial rRNAs, it is likely that the accreted proteins do not interact directly with the rRNA moiety. 

Figure 7 The effect of varying concentration of trehalose, while maintaining a constant sugar/protein mass ratio, on recovery of phosphofructokinase (PFK) activity after freezedrying and rehydration. The protein concentration was adjusted concomitantly with the sugar concentration to maintain a constant sugar/protein mass ratio of 945. (Data taken from Ref. 59.)...

FIG. 16 Sketch of an integral membrane protein complexed by amphiphilic short polymers (amphipols). Protein and polymers are drawn to scale. The polymer/protein mass ratio corresponds to a typical experimental value of 1. The persistence length of the amphipol has been taken equal to about 3 nm. The number of contacts among the partners is largely speculative. (Reprinted from Ref. 3. Copyright 1996 National Academy of Sciences, U.S.A.)... 

Misunderstandings arise when membrane users assume that MWCO means what it seems to say. The definition implies that a 50 kD membrane will separate a 25 kD material from a 75 kD material. The rule of thumb is that the molecular mass must differ by a factor of ten for a good separation. Special techniques are used to permit the separation of proteins with much smaller mass ratio. 

In an ideal pure preparation of Na,K-ATPase from outer renal medulla, the al subunit forms 65 70% of the total protein and the molar ratio of a to is 1 1, corresponding to a mass ratio of about 3 1 [1,5]. Functionally the preparation should be fully active in the sense that each a/ unit binds ATP, Pj, cations and the inhibitors vanadate and ouabain. The molecular activity should be close to a maximum value of 7 000-8 000 Pj/min. The highest reported binding capacities for ATP and phosphate are in the range 5-6 nmol/mg protein and close to one ligand per otjS unit [29], when fractions with maximum specific activities of Na,K-ATPase [40 50 pmo Pj/min mg protein) are selected for assay. 

The feasibility of this approach to not only differentiate pathogenic and nonpathogenic strains of bacteria based on significant differences in protein mass but also on the basis of variations in levels of protein expression was demonstrated using a method for quantitating protein expression by LC/MS of whole proteins.54 This method is based on the fact that some proteins present in cells are abundant universal proteins whose expression levels exhibit little variation. This method demonstrates that these co-extracted proteins can be used as internal standards to which the other proteins in the sample can be compared. By comparing the intensities of a selected protein to a marker protein, or internal standard, a relative ratio is obtained. This ratio... 

Variations on the spectral peaks from different species of the same genus were also observed. Three species of Pseudomonas produced the spectra shown in Figure 14.2. These spectra are clearly unique and were used to correctly identify unknown samples. Because of peak ratio reproducibility issues in bacterial protein profiles obtained by MALDI MS,11 a fingerprint approach that had been used for other mass spectrometry approaches has not been used. The profile reproducibility problem was first recognized by Reilly et al.12,13 and later researched by others in the field.14,15 As a later alternative, a direct comparison of the mass-to-charge ratio (m/z) of the unknown mass spectral peaks with a database of known protein masses has been used to identify unknown samples.14... 

Molar mass determinations based on SDS-PAGE is sometimes misleading, since some proteins are not conversed completely into a rod-like shape or the protein/SDS ratio differs from the average. 

Distribution is the delivery of drug from the systemic circulation to tissues. Once a drug has entered the blood compartment, the rate at which it penetrates tissues and other body fluids depends on several factors. These include (1) capillary permeability, (2) blood flow-tissue mass ratio (i.e., perfusion rate), (3) extent of plasma protein and specific organ binding, (4) regional differences in pH, (5) transport mechanisms available, and (6) the permeability characteristics of specific tissue membranes. 

In MALDI MS, the analyte is additionally embedded in higher molar excess of matrix molecules, which allows a soft desorption and ionization of the analyte. Typical molar ratios between the matrix and the analyte for measurement of low-molecular weight compounds (<500 Da) are in the range between 10 1 and 100 1, for higher masses (e.g., peptides and proteins) typical ratios are in the range of 1000 1 up to 100,000 1. Despite the capability to be measured by LDI MS, most classical ILs based on pyridinium... 

Figure 3.2 Evolution of the microstructure of phase-separated biopolymer emulsion system containing pectin and 0.5 vt% heat-denatured (HD) whey protein isolate (WPI) stabilized oil droplets, (a) Composition 1U 3L (one-to-three mass ratio of upper and lower phases). The large circles are the water droplets (W), while the small circles are the oil droplets (O). This system forms a W2/W1-O/W1 emulsion, where O is oil, Wi is HD-WPI-rich and W2 is pectin-rich, (b) Composition 2U 2L. This system forms an 0/Wi/W2 emulsion, where O is oil, Wi is HD-WPI-rich and W2 is pectin-rich, (c) Composition 3U 1L. This system forms an 0/W]/W2 emulsion, where O is oil, Wi is HD-WPI-rich and W2 is pectin-rich. Reproduced from Kim et al. (2006) with permission.

Electrophoresis of proteins is generally carried out in gels made up of the cross-linked polymer polyacrylamide (Fig. 3-19). The polyacrylamide gel acts as a molecular sieve, slowing the migration of proteins approximately in proportion to their charge-to-mass ratio. Migration may also be affected by protein shape. In electrophoresis, the force moving the macromolecule is the electrical potential, E. The electrophoretic mobility of the molecule, g, is the ratio of the velocity of the par-... 

Now, when the ionic front reaches the lower gel with pH 8 to 9 buffer, the glycinate concentration increases and anionic glycine and chloride carry most of the current. The protein or nucleic acid sample molecules, now in a narrow band, encounter both an increase in pH and a decrease in pore size. The increase in pH would, of course, tend to increase electrophoretic mobility, but the smaller pores decrease mobility. The relative rate of movement of anions in the lower gel is chloride > glycinate > protein or nucleic acid sample. The separation of sample components in the resolving gel occurs as described in an earlier section on gel electrophoresis. Each component has a unique charge/mass ratio and a discrete size and shape, which directly influence its mobility. 

This mass dependence study can be extended to investigate the dependence of the relaxation processes in proteins on the solvent viscosity. Experimentally, this has been studied by changing the molecular composition of the solvent [110, 111], thus changing the solute-solvent mass ratio. Hence the theoretical analog of this experimental study will be to investigate the dependence of the relaxation processes in proteins on solute-solvent mass ratio. 

Davidson, P., Sun, W.Q. Effects of su-crose/raffinose mass ratios on the stability of co-lyophilized protein during storage above Tg. Pharm. Res. 18, 474-479, 2001... 

The impact of parameters such as the ratio of protein mass to the membrane cutoff (A), or the effect of the membrane material during permeation, on their structure/ function, is currently unknown and constitutes an essential requisite for the full development and implementation of membrane processes for the selective fractionation of proteins. 

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