Fast labeling

Acoustophoresis needs to be a process so robust and efficient that it can be used as an alternative safe (causing less shear on cells), economical, and fast (label-free) cell separation method for diagnostics and therapeutic medical applications. In order to increase the robustness of ultrasonic separation process, it is important that parameters that improve the performance are well understood and optimized. Numerical simulations... 

The clearest demonstration of the temporal sequence of synthesis of different forms of virus-specific messenger RNA has been given by the work of Becker and Joklik (1964), who studied synthesis of fast-labeled RNA in HeLa cells infected with vaccinia virus. 

Hydrolysis of the nucleohistones with trypsin caused a sharp increase in the rate of synthesis of RNA and proteins in thymus nuclei. In interphase nuclei of thymus lymphocytes the repressed nucleohistone zones were concentrated mainly in condensed heterochromatin masses, whereas active interphase DNA was found in euchromatin fibrils (Frenster et al., 1963). A large part of the fast-labeled nuclear RNA was found in these fibrils. 

Comparatively recently a sharp increase in activity of a number of liver enzymes in rats and other animals is produced by cortisone (Knox et al., 1956). This stimulation of enzyme (glutamate-tyrosine transaminase, tryptophan-pyrrolase, glucose-6-phosphatase, etc.) activity by cortisone in experiments on adrenalectomized rats was associated with the synthesis of these enzymes de novo (Kenney, 1962 Alievskaya, 1965). As might be expected, this increase in enz5mie synthesis was preceded by a sharp increase in synthesis of RNA, particularly RNA of the cell nuclei (Fig. 99) (Kenney and Kull, 1963). The RNA fraction which was stimulated corresponded in its sedimentation characteristics to fast-labeled (messenger) RNA. 

Figure A3.5.L The fast ion beam photofragment spectrometer at SRI International. L labels electrostatic lenses, D labels deflectors and A labels apertures.

In many cases the dynamical system consists of fast degrees of freedom, labeled x, and slow degrees of freedom, labeled y. An example is that of a fluid containing polyatomic molecules. The internal vibrations of the molecules are often very fast compared to their translational and orientational motions. Although this and other systems, like proteins, have already been treated using RESPA,[17, 34, 22, 23, 24, 25, 26] another example, and the one we focus on here, is that of a system of very light particles (of mass m) dissolved in a bath of very heavy particles (mass M).[14] The positions of the heavy particles are denoted y and the positions of the light particles rire denoted by X. In this case the total Liouvillian of the system is ... 

The often fast binding step of the inhibitor I to the enzyme E, forming the enzyme inhibitor complex E-I, is followed by a rate-determining inactivation step to form a covalent bond. The evaluation of affinity labels is based on the fulfillment of the following criteria (/) irreversible, active site-directed inactivation of the enzyme upon the formation of a stable covalent linkage with the activated form of the inhibitor, (2) time- and concentration-dependent inactivation showing saturation kinetics, and (3) a binding stoichiometry of 1 1 of inhibitor to the enzyme s active site (34). 

The hydrazinolysis is usually conducted in refluxing ethanol, and is a fast process in many cases. Functional groups, that would be affected under hydrolytic conditions, may be stable under hydrazinolysis conditions. The primary amine is often obtained in high yield. The Gabriel synthesis is for example recommended for the synthesis of isotopically labeled amines and amino acids. a-Amino acids 9 can be prepared by the Gabriel route, if a halomalonic ester—e.g. diethyl bromomalonate 7—is employed as the starting material instead of the alkyl halide ... 

In contrast to PEG-1000, the ESR-spectra obtained for labelled grafted PEO-oligomers (N = 1-9) were reported to differ strongly from that for N = 23 and exhibited only slowly moving labels. As the fine width of the fast domain spectrum depends on the mobility of the label, it can be concluded that the tails for N = 23 must consist of at least 4-9 repeated units. It appears that some tails are rather long. 

The differences in rate for the two positions of naphthalene show clearly that an additional-elimination mechanism may be ruled out. On the other hand, the magnitude of the above isotope effect is smaller than would be expected for a reaction involving rate-determining abstraction of hydrogen, so a mechanism involving significant internal return had been proposed, equilibria (239) and (240), p. 266. In this base-catalysed (B-SE2) reaction both k and k 2 must be fast in view of the reaction path symmetry. If diffusion away of the labelled solvent molecule BH is not rapid compared with the return reaction kLt a considerable fraction of ArLi reacts with BH rather than BH, the former possibility leading to no nett isotope effect. Since the diffusion process is unlikely to have an isotope effect then the overall observed effect will be less than that for the step k. ... 

The fast reaction clearly involves the transition state (XLVIII) as confirmed by the observation of Reutov etal.123 that all of the label in the mercuric bromide... 

One may gain insight to this matter by referring to the time scale of a given step, defined as its lifetime, l/k. The time scale for the first step is (ki + fc-i)-1. For the second it is lA2. Since k2 k-1, the label fast, applied to the second step, is understandable in this sense. 

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