Restriction molecular mass

The molecular mass of the protein was redetermined by infusing a 5-10 pmolp.l solution of the protein in 50% aqueous acetonitrile containing 0.2% formic acid at a flow rate of 6 p,lmin into an electrospray source. The scan rate employed on the mass spectrometer was from m/z 60 to m/z 1800 in 12 s. This is a relatively slow scan speed which will lead to a more precise molecular weight determination. Scan speeds of this order may be, and indeed should be, utilized for infusion experiments if sufficient sample is available but it is unlikely to be feasible when chromatographic separations, particularly those involving capillary columns, are employed because of the restriction imposed by the chromatographic peak width (see Section 3.5.2.1 above). 

Although the absolute configurations of the products are opposite to that of antiinflammatory active compounds, and the substrate specificity is rather restricted as to the steric bulkiness around the reaction center, the enzyme system of A. bronchisepticus was proved to have a unique reactivity. Thus, detailed studies on the isolated enzyme were expected to elucidate some new interesting mechanism of the new type of decarboxylation. Thus, the enzyme was purified. (The enzyme is now registered as EC 4.1.1.76.) The molecular mass was about 24kDa. The enzyme was named as arylmalonate decarboxylase (AMDase), as the rate of the decarboxylation of phenylmalonic acid was faster than that of the a-methyl derivative. ... 

Restricting to the more common elements in organic mass spectrometry (H, B, C, N, O, Si, S, P, F, Cl, Br, I, etc.), a simple rule holds valid With the exception of N, all of the above elements having an odd number of valences also possess an odd mass number and those having an even number of valences have even mass numbers. This adds up to molecular masses fulfilling the nitrogen rule (Tab. 6.7). 

It is worthwhile pointing out another issue at this juncture. The low molecular-mass selectors can be grafted onto the surface of mesoporous silica (usually equal to 10 nm pore diameter) in a relatively high molar selector concentration due to their restricted space requirements (yielding typical selector loadings of about 0.4mmolg CSPcorrespondingtoca. 1.3 p,molm ). As a consequence, arelatively... 

Unfortunately, this field is made difficult for a student by the terminology used by biochemists. For example, there is a protein kinase that regulates the cycle between G2 and M, i.e. the second restriction point. This protein is known as maturation (or mitosis) promoting factor, since it promotes entry into mitosis. It phosphorylates a protein, probably a transcription factor, in the nucleus. The kinase has a molecular mass of 34kDa. Hence it is known as p34 cell division kinase, abbreviated to p34-cdc and, since it is regulated at restriction point 2, it is known as p34-cdc-2 protein, which is sometimes written as p34°. This kinase is normally inactive until it binds a cyclin. Hence the active maturation-promoting factor is, in fact, a protein kinase-cyclin complex, which is referred to as p34° °-cyclin complex. It is hoped that this piece of information may help a student (or lecturer from another field) to understand one part of a review article that contains the abbreviation p34° -cyclin complex, without explanation, or other similar pieces of biochemical shorthand. 

Cellular uptake of AS-ODNs is restricted because of their large molecular mass as well as their polyanionic character. When added directly to cells in culture, only 1-2% of the AS-ODNs will be cell-associated. Therefore, enhanced AS-ODN uptake is a critical consideration in developing these agents for therapeutic applications. 

The applicability of the APCI interface is restricted to the analysis of compounds with lower polarity and lower molecular mass compared with ESP and ISP. An early demonstration of the potential of the APCI interface is the LC-APCI-MS-MS analysis of phenylbutazone and two of its metabolites in plasma and urine (128). Other applications include the LC-APCI-MS analysis of steroids in equine and human urine and plasma (129-131), the determination of six sulfonamides in milk samples after a simple solid-phase extraction and LC separation (132), of tetracyclines in muscle at the 100 ppb level (133), of fenbendazole, oxfendazole, and the sulfone metabolite in muscle at the 10 ppb level, and of five thyreostats in thyroid tissue at the 1 ppm level (134). 

The translational entropy is high about 120 J/deg/mol (30 cal/deg/mol) for a 1 -M solution of a small molecule. This is equivalent to about 40 kJ/mol (9 kcal/mol) at 25°C (298 K). The translational entropy is proportional to the volume occupied by the molecule the smaller the volume, the more the molecule is restricted and the lower the entropy. Similarly, the entropy decreases with increasing concentration, since the average volume occupied by a molecule is inversely proportional to its concentration. It is important to note that the dependence on mass is low (Table 2.3). A 10-fold increase in mass on going from, say, a relative molecular mass of 20 to one of 200 leads to only a small increase in translational entropy. 

If we take into consideration that the lowest experimentally possible polyelectrolyte concentration cp is approximately 10 6 monomol L 1, it follows from Table 8 that the diluted solution state, cp 2000, i.e. if Mn >320,000 g-mol The theoretical treatment and the experimental studies of the concentration dependent behavior of polyelectrolytes in solution is usually restricted to the case with or without an excess of a low molecular electrolyte. A relatively limited amount of data exist for similar concentrations of polyelectrolytes and low molecular mass salt [97]. 

The following molecular constants are used in further calculations density p of a liquid the static (es) and optical (n ) permittivity moment of inertia /, which determine the dimensionless frequency x in both HC and SD models the dipole moment p the molecular mass M and the static permittivity 1 referring to an ensemble of the restricted rotators. The results of calculations are summarized in Table XXIII. In Fig. 62 the dimensionless absorption around frequency 200 cm 1, obtained for the composite model, is depicted by dots in the same units as the absorption Astr described in Section B. Fig. 62a refers to H2O and Fig. 62b to D2O. It is clearly seen in Fig. 62b that the total absorption calculated in terms of the composite model decreases more slowly in the right wing of the R-band than that given by Eq. (460). Indeed, the absorption curve due to dipoles reorienting in the HC well overlaps with the curve generated by the SD model, which is determined by the restricted rotators. 

Lyons and Tobolsky successfully applied Eq. (16.33) to the systems poly(propylene oxide)-benzene and poly(propylene oxide)-methylcyclohexane. The application was restricted, however, to a polymer of molecular mass 2000, which is below the critical molecular mass Mcr. 

A certain generalisation is permitted with respect to the relationship between the effects of concentration and molecular mass on the viscosity of polymer solutions. It is restricted to solutions of polymers with M > Mcr in good solvents. 

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