Single preparation

G.16 To prepare a very dilute solution, it is advisable to perform successive dilutions of a single prepared reagent solution, rather than to weigh out a very small mass or to measure a very small volume of stock chemical. A solution was prepared by transferring 0.661 g of K2Cr20- to a 250.0-mL volumetric flask and adding water to the mark. A sample of this solution of volume 1.000 mL was transferred to a 500.0-mL volumetric flask and diluted to the mark with water. Then... 

Gusarova, N.K., Shaikhudinova, S.I., Dmitriev, V.I., Malysheva, S.F., Arbuzova, S.N., and Trofimov, B.A., Reaction of red phosphorus with electrophiles in superbasic systems. VII. Phospholanes and phosphorinanes from red phosphorus and a,co-dihaloalkanes in a single preparative step, Zhur. Obshch. Khim., 65, 1096, 1995. 

Figure 17.3 Effects of endothelin-1 (ET-1) on NBDL-CSA (P-glycoprotein substrate) transport in isolated capillaries. (A) Concentration-dependent decrease in steady-state luminal NBDL-CSA accumulation caused by ET-1. (B) Effect of ET-1 on steady-state luminal NBDL-CSA accumulation. Capillaries were loaded to steady state in medium with 2 /xM NBDL-CSA. Then, 100 nM ET-1 was added to the medium (time 0 on graph) 90 min later, ET-1 was removed. Each point represents the value for 7-15 isolated capillaries from a single preparation (tissue from 3 to 10 rats). Variability is given by S.E. bars. Units are arbitrary fluorescence units. Statistical comparison , significantly smaller than control, P < 0.0001 (with permission from 75).

For the extraction of sulfates and total sulfur a suitable acid and reducing agent, such as tin(II)-phosphoric acid (the Kiba solution of Sasaki et al. 1979) is needed. The direct thermal reduction of sulfate to SO2 has been described by Holt and Engelkemeier (1970) and Coleman and Moore (1978). Ueda and Sakai (1984) described a method in which sulfate and sulfide disseminated in rocks are converted to SO2 and H2S simultaneously, but analyzed separately. With the introduction of on-line combustion methods (Giesemann et al. 1994), multistep off-line preparations can be reduced to one single preparation step, namely the combustion in an elemental analyzer. Sample preparations have become less dependent on possibly fractionating wet-chemical extraction steps and less time-consuming. 

A combination vaccine consists of two or more separate immunogens physically combined in a single preparation. A combination vaccine gives protection from more than one disease. 

Figure 32. Time course of generation of 5 -ATP-induced membrane potential and disappearance of the membrane potential by adding a specific inhibitor ouabain for a single preparation of Na, K -ATPase-based BLM. 5 -ATP was injected into the cis side solution (final concentration 10 mM) and ouabain (DMSO solution) into the trans side solution (final concentration 1 mM) (reprinted with permission from Anal. Chim. Acta 1993, 281, 583. Copyright 1993 Elsevier Science Ltd.).

No doubt, heterocyclizations of 311 to 316 and 311 to 333 are the most complicated transformations, based on nucleophilic substitution of hydrogen, known at present. In spite of moderate yields, the method permits one to obtain in a single preparation step compounds that are otherwise very hard to obtain. Another feature is that for the first time an oxidant serves here not only for aromatization of oH-adducts but also for modification of both reactants before each next stage. This tremendously expands the synthetic possibilities of such reactions that obviously need further extensive development. 

Arylated cyclopentadienes, especially pentaarylcyclopentadienes 6, have interesting properties as ligands for transition metals [1] or as electroluminescent materials [2], The classical methods for their preparation are multistep procedures [3], which are somewhat tedious and usually less suitable for sterically demanding aryl groups. In contrast, the palladium-catalyzed arylation of either metallocenes such as zirconocene dichloride (1) or simply cyclopentadiene (3) with aryl halides leads to the target compounds 4—6 in a single preparative step (Scheme 1) [4—6]. 

Use of Time in Laboratory. In preparation work it is frequently necessary to wait for considerable periods of time for evaporations, crystallizations, etc., to take place. This time may be utilized for work upon the study questions and experiments, but even then it is advisable to have usually more than a single preparation under way. Thus no time need be wasted by the energetic student who plans his work well. A program of work should be made out in advance of the laboratory exercise. 

For each of the above protocols paired measurements of one or several given parameters of tubule transport are obtained under control conditions and in the presence of a substance under study. Also concentration response curves can be obtained in one single preparation (Schlatter et al. 1983 Wangemann et al. 1986 Wittner et al. 1987). Intracellular measurements are usually required to define the mechanism of action (Greger 1985). Especially the electrical and optical measurements have a very high reproducibility. For screening usually 3 preparations are sufficient. Approximately 10 preparations are required for concentration response curves. 

Photolysis of 36 in the presence of the carbonyl-protected alanine derivative 37 allows the diastereoselective assembly of the dipeptide 38 in a one pot synthesis [13]. This process is remarkable for several reasons on the one hand the peptide bond and one new stereogenic center are established in a single preparative step on the... 

It is well known that the O2 reduction site of bovine heart cytochrome c oxidase in the fuUy oxidized state exhibits variable reactivity to cyanide and ferrocytochrome c, which is dependent on the method of purihcation (Moody, 1996). Some preparations react with cyanide extremely slowly at an almost immeasurable rate and are known as the slow form. Other preparations, which react at a half-Ufe of about 30 s, are known as the fast form (Brandt et al., 1989). Electronic absorption spectra of the slow-and fast-form preparations exhibit Soret bands at 418 and 424 nm, respectively. The two forms often coexist in a single preparation (Baker et al., 1987). Both forms exhibit an identical visible-Soret spectrum in the fully reduced state. The slow-form preparation can be converted to the fast form by dithionite reduction followed by reoxidation with O2. The fast form thus obtained returns to the slow form spontaneously at a rate much slower than the enzymatic turnover rate. Thus, the slow form is unlikely to be involved in the enzymatic turnover (Antoniniei a/., 1977). It should be noted that no clear experimental evidence has been reported for direct involvement of the fast form in the enzyme turnover, although its direct involvement has been widely accepted. The third species of the fully oxidized O2 reduction site, which appears in the partially reduced enzyme, reacts with cyanide 10 —10 times more rapidly than the fast form (Jones et al., 1984). In the absence of a reducing system, no interconversion is detectable between the slow and the fast forms (Brandt et al., 1989). Thus, the heterogeneity is expected to inhibit the crystallization of this enzyme. In fact, the enzyme preparations providing crystals showing X-ray diffraction at atomic resolution are the fast form preparation. 

Since the titer of antiserum changes from animal to animal and within the same animal with time, it is advisable to use a single preparation for each set of experiments. When this is not possible each new preparation must be completely standardized. In the case of the secondary antibody preparation, only its ability to precipitate the primary antibodies must be quantitated. Primary antibody preparations, however, must be titrated for their ability to serve as both antibodies and antigens. 

Two limiting cases could be considered that would, however, let us treat in a simple way the interfacial electron transfer process as involving a single prepared excited state of the sensitizer ... 

Many of the listed functions/properties of liposomes, such as longevity, targetability, stimuli-sensitivity, ability to deliver drugs intracellularly, etc. could, theoretically, be combined in a single preparation yielding a so-called multifunctional liposomal nanocarrier (155) (see Fig. 1). 

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