Sensitivity derivation

These water-sensitive derivatives can be used to form cleanly the t-butyl ethers of serine and threonine. They are cleaved with aqueous acid or base. ... 

Sensitivity, derivative of the measured quantity (response) y with respect to the analytical quantity x Total multicomponent sensitivity... 

The procedure provides a sensitive derivative for analysis of Diclofopmethyl and of its hydrolysis product by gas-liquid chromatography. Standards of the derivative, stored in hexane at room temperature, were stable for at least one month. The method is rapid and permits the detection of 0.05mg kg-1 of diclofop in soil with minimum interference from coextractives. The alkylation product also provides a second method for verification of diclofop by gas-liquid chromatography. 

Alvarez MG, Prucca C, Milanesio ME, Durantini EN, Rivarola V (2006) Photodynamic activity of a new sensitizer derived from porphyrin-C60 dyad and its biological consequences in a human carcinoma cell line. Int J Biochem Cell Biol 38 2092-2101. 

The derivatization of fatty acids, and of acidic substances in general, has been a problem in analytical-organic chemistry for many years. The classically used derivatives have been amides and esters. The main problem in using methyl esters of fatty acid in HPLC is that one cannot then use the UV detector, because of inadequate absorption. Thus a search for an alternate method of forming UV-sensitive derivatives has been initiated in several laboratories. 

The fragmentation leads to the simultaneous generation of two neutral radicals in close proximity, separated only by the carbonyl product. Depending on the nature of the substrate, these fragments may react by hydrogen atom transfer, either to the aminoalkyl (benzyl) radical or to the sensitizer derived radical. Accordingly, the acceptor can act either as a sensitizer or undergo two-electron reduction. 

Note NMR properties of the most commonly used nuclei in in vivo NMR. The relative sensitivity derives from the physical properties of the nucleus, whereas the absolute sensitivity is the product of the relative sensitivity and the natural abundance of the isotope. 

The direct selenenylation technique is well suited to ketones that are not acid labile but cannot be applied to acid-sensitive derivatives however, in such cases an alternative procedure which employs basic conditions is commonly used. The ketone is first converted to the lithium enolate, usually with lithium diisopropylaniide, and then selenenylated with phenylselenenyl chloride or bromide or diphenyl diselenide8. 

Remarkable advances have been made in the synthesis of N- and O-glycosylated amino acids that, in addition to the 5-fattyacyl-cysteine, are the most sensitive derivatives to the conditions of peptide synthesis. The fine tuning of both carbohydrate and peptide chemistry as well as the use of enzymatic methods are required for the synthesis of glycopeptides. " Similarly soft chemistry has to be applied in the case of S-acylated peptides, whereas fat-tyacylation at amino groups raises no additional difficulties.The state of the art in the field of glyco- and lipopeptide synthesis is discussed in details in Vol. E22b, Sections 6.3 and 6.4, respectively. 

Only the methods used in this study (i, 2, 3) can detect and follow the initial events at the boundary between a solid substrate and the biological milieu. This extraordinary sensitivity derives from the ability to monitor events from within the substrate itself by making the substrate capable of supporting multiple attenuated internal reflection (MAIR) at a variety of useful spectroscopic wavelengths. In other studies, it was concluded that adsorbed protein on solid substrates is of essentially native i.e. solution or volume phase) conflguration and present in signiflcant thickness (6). Those studies used a different version of the internal reflection spectroscopic method wherein a prism element was forcefully... 

Besides the many acid sensitive derivatives, base labile protecting groups for 1,2-diols were also recommended. With phosgene or a chlorofoimate, cyclic carbonates are formed from cis- and trans-diols. They are stable to the conditions that hydrolyze acetals but are readily removed by saponification. (Tyclic boronates may also be used, but their application is limited because they hydrolyze very rapidly... 

To these species the structure of air currents is not invisible. A considerable portion of their brains has evolved to process information from their whiskers (or vibrissae), and one may plausibly suggest that their olfactory sensitivity derives, at least in part, from the ability to monitor the structure of air and to situate a scent within the currents that eddy about their snouts (Cain, et al., 1985). If, even in the absence of vibrissae, human olfaction can, nevertheless, sense the heterogeneity of odors, this adds another complexity to our experience of smell. As argued above, diffusion through mucus limits the temporal resolution of olfaction to about 0.1 second. If humans have the capacity... 

This protocol has been successfully applied to primary, secondary and tertiary aliphatic carboxylic acids encompassing a wide range of functionality. Some illustrative examples are shown below in Scheme 6 and include the sensitive derivative 6 [11] (where all classical Hunsdiecker variants were unsuccessful) and the fragile a-halooxetane 7 reported by the Fleet group [12],... 

For this purpose detectable levels in the range of 1 pg per ml of plasma are needed. In order to achieve this sensitivity it is necessary to make a fluorescent derivative of sulfisoxazole. One such derivative is the highly fluorescent "Dansylsulfonamlde" which is formed by the reaction shown in Figure 9. The fluorescence yield of this compound is sufficient to measure about 1 yg of sulfisoxazole per ml of plasma. An even more sensitive derivative is formed when sulfisoxazole is reacted with 4,5-methylene-dioxy-phthalaldehyde to form a phthalimidine derivative (Figure 9). The sensitivity limit for this derivative is from 1 X 10 to 1 X 10 10 mole/ml (22). 

The resolution of the system is moderate and the stability after irradiation is poor. However, it is used for the 243 nm domain due to its sensitivity. Derivatives of this resist system have also been proposed, e.g., a copolymer of 4-hydroxystyrene with a r-butyl acrylate and a phenyloxysuccinimid as the acid photogenerator. This resist is more stable during processing (Figure 6.16). 

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