Media depletion

An interesting variation on the whole-cell MALDI approach was recently reported in a study aimed more at FTMS than TOF MS, but the results are nevertheless interesting and important to users of both methods for analysis of bacteria 40. Wilkins s group showed both MALDI-TOF and MALDI-FTMS spectra of whole bacteria grown on isotopic media depleted in C13 and N14. Because most bacterial identification protocols involve a culture step prior to analysis, it is possible to manipulate the sample based on control of the growth media. For mass spectral analysis manipulation of the isotope profile... 

Onr previons experiments with the modihed media depleted of varions chemicals demonstrated that some of them might inhibit HRF. Next, we hypothesized that enrichment of the growth medium with these chemicals can enhance HR. To test this hypothesis, we grew Arabidopsis plants on the modified medium supplemented with varions concentrations of chemicals chosen for the experiment. These chemicals were named G and H. The standard MS medium served as the control. HRF was analyzed 3 weeks postgermination. 

Determination of the amount and distribution of amino acids is required for a variety of bioanalytical questions. In bioprocess monitoring, the amount of certain free amino acids has to be monitored in order to avoid media depletion. In the case of a protein or a protein hydrolysate, analysis or verification of the amino acid composition may be a first step toward identification or characterization. The early work on amino acid analysis has been dominated by Stein and Moore, who in 1972 were awarded the Nobel prize... 

A small amount of sodium dithionite added to an aqueous medium depletes oxygen almost instantly. Due to the acidity of the reagent, a sufficiently strong buffer must be included in the medium. However, the use of dithionite is not recommended in the stages of extraction and purification because the reagent and its decomposition products are highly reactive and can cause undesirable reactions. 

The use of CIEF in combination with FTICR has been demonstrated in an analysis of the E. coli proteome (Jensen et al., 1999). For these experiments, E. coli was grown in a medium depleted of rare isotopes in order to increase the mass measurement accuracy. The high abundance isotopes are present at approximately 98.89% 12C, 99.63% 14N and 99.985% H. For peptides, the presence of rare isotopes does not significantly change the spectra but with undigested proteins, mass accuracy can be limited by the broadened distribution of ions of any given protein due to the incorporation... 

Darby, C. R., Hamano, K., and Wood, K. J. (1993). Purification of monoclonal antibodies from tissue culture medium depleted of IgG.. Immunol. Methods 159, 125-129. 

As we have discussed earlier in the context of surfaces and interfaces, the breaking of the inversion synnnetry strongly alters the SFIG from a centrosynnnetric medium. Surfaces and interfaces are not the only means of breaking the inversion synnnetry of a centrosynnnetric material. Another important perturbation is diat induced by (static) electric fields. Such electric fields may be applied externally or may arise internally from a depletion layer at the interface of a semiconductor or from a double-charge layer at the interface of a liquid. 

Many aromatic compounds are sufficiently basic to be appreciably protonated in concentrated sulphuric acid. If nitration occurs substantially through the free base, then the reactivity of the conjugate acid will be negligible. Therefore, increasii the acidity of the medium will, by depleting the concentration of the free base, reduce the rateof reaction. This probably accounts for the particularly marked fall in rate which occurs in the nitration of anthraquinone, benzoic acid, benzenesulphonic acid, and some nitroanilines (see table 2.4). 

A typical fermentation medium for penicillin production contains lactose, com steep Hquot, and calcium carbonate (3,153,154). In most industrial processes the carbohydrate source, glucose, beet molasses, or lactose, is continuously added to the fermentation. The rate of glucose addition must be carefully monitored, by pH or rate of oxygen depletion, because the synthesis of penicillin is markedly reduced in the presence of excess glucose. 

Problems that rank relatively high in duee of the four typos, or at least medium in all four, include criteria air pollutiuits, stratospheric ozone depletion, pesticide residues on food, and other pesticide risks (runoff and air deposition of pesticides)... 

The equation for displacement of a radioligand [A ] by a nonradioactive ligand [B] can be rewritten in terms of one where it is not assumed that receptor binding does not deplete the amount of radioligand in the medium (no change in [A free]) ... 

At temperatures of the order 700 - 900 K the surface point defects play the dominant role in controlling the various eledrophysical parameters of adsorbent on the content of ambient medium [32]. As it has been mentioned in section 1.6, these defects are being formed in the temperature domain in which the respective concentration of volume defects is very small. In fact, cooling an adsorbent down to room temperature results violation of uniform distribution due to redistribution of defects. The availability of non-homogeneous defect distribution led to creation of a new model of depleted surface layer based on the phenomenon of oxidation of surface defects [182] which is an alternative to existing model of the Shottky barrier [183]. 

Recently, another interaction was reported between an intracellular pathogen and the key regulator system of intracellular iron concentration, i.e. the degree of binding of the IRPs to IRE (see Chapter 7). In extracts from Leishmania tarentolae, a protein has been detected that binds specifically to the mammalian IRE. However, the exact nature and function of this protein is unclear up to now. In contrast to mammalian IRPs, the L. tarentolae IRE-binding activity was not induced by growth in iron-depleted medium (Meehan et ah, 2000). 

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