High-concentration labeling

Here we consider how to obtain the single-particle form factor even when labeled molecules are present at a high concentration. For this purpose let us first consider a single-component, bulk polymer, consisting of N molecules in volume Vy each molecule with Z = v/vu segments. The amplitude of scattering from such a polymer is 

We define the single-particle (or intramolecular) form factor P(q) by 

Separating intramolecular from intermolecular contributions, we can then write Equation (6.60) as 

In most instances it is the form factor P q) that we wish to determine. The form factor gives information about the average shape of the molecule. Suppose we have a blend of hydrogenous and deuterated polymers, both having the same chemical structure and the same number of segments, Z, per molecule, and their volume fractions are 0h and 0D, respectively (0h + 0d = 1). In the blend there are thus TVh = Ncj h hydrogenous molecules and N = N0d deuterated molecules, and instead of (6.63) the scattering intensity is now written as 

67) the average scattering lengths, (b2) for the P(q) term and (b)2 for the Q(q) term, depend differently on 0D. Therefore, when measurements are made at two different concentrations of labeled polymers, a set of two simultaneous linear equations (6.67) with two unknowns P q) and Q(q) is obtained, which can then be solved readily (Williams etal.n and Akcasu et al.12). 

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Rates of alkaloid labelling are very similar under pulse and chase conditions (cf. data in table). In contrast chase labelling of the protein fraction is lacking in samples pulsed vith 4 and 19 /Ug/ml L-Phe. It can be found only in discs on 50 /Ug/ml L-Phe (cf. Table, values in square). It appears that for phenylalanine released from expandable pool the opposite holds true as for phenylalanine entering cells from outsides radioactivity is preferably incorporated into alkaloids and only at rather high concentrations labelling of proteins becomes measurable. 

Contrast and deuterium labeling 7.3.1 High-concentration labeling... 

Provide fire suppression deluge protection in areas having high concentrations of flammables or combustibles Test reactive and critical raw materials prior to use Sample to confirm concentrations Label all containers... 

One of the best-studied carrier molecules is produced as a primary excretory constituent of the adult male mouse, known from its consistent high concentration as the major urinary protein (MUP). The basic 3-D structure of the protein was initially obtained from a monoclinic crystal of recombinant protein (MUP-I), constructed by induction in a bacterial expression system and purified to homogeneity (Kuser, 1990). A wild type version of MUP finally yielded to NMR analysis a clone of the r-isoform (162 residues) was labelled and compared with the crystal-structure (Lucke et al., 1990). Two views of the molecule... 

Figure 3.10 Concentration of labeled compound I bound to an enzyme as a function of the concentration of a second inhibitor J. (A) Response of bound I to concentration of / when I and / bind in a mutually exclusive fashion. Note that here the concentration of the bound I is driven to zero at high concentrations of J. (B) Response of bound I to concentration of J when the two compounds bind in a nonexclusive, antagonistic manner to the target enzyme. Note that at high concentrations of J one does not drive the concentration of bound I to zero. Rather, the concentration of bound I at high concentrations of /reflects the concentration of ternary E I J complex. Condition of simulations I IK, = 1 (closed circles), 3 (open circles), and 5 (closed squares). For panel B, y = 5.

Bisulfite modification of cytosine residues also can be used to add permanently a sulfone group to the C-6 position. In this scheme, the sulfone functions as a hapten recognizable by specific anti-sulfone antibodies. At high concentrations of bisulfite and in the presence of methyl-hydroxylamine, cytosines are transformed into N4-methoxy-5,6-dihydrocytosine-6-sulphonate derivatives (Herzberg, 1984 Nur et al., 1989). Labeled antibodies can then be used to detect the hybridization of such probes. 

The same group reported the simultaneous radiolabeling (with DOTA-anchored 4Cu) and fluorescence studies, coupled with biodistribution in vivo and in vitro (92). It is believed that appropriately functionalized SWNTs can efficiently reach tumor tissues in mice with no apparent toxicity (159). Furthermore, water-solubilised carbon nanotubes are nontoxic when taken up by cells even in high concentration (92). These studies have been complemented by the recent PET imaging of water-soluble 86Y labelled carbon nanotubes in vivo (mice) (160,161), to explore the potential usefulness of carbon nanocarriers as scaffolds for drug delivery. The tissue biodistribution and pharmacokinetics of model DOTA functionalized nanotubes have been explored in vivo (mouse model). MicroPET images indicated accumulation of activity mainly in the kidney, liver, spleen, and to a much less... 

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