Acid quencher

All data obtained with Tecan Ultra Evolution MTP reader. The following excitation and emission wavelengths were used EDANS and AMC 350 and 500 nm RhllO 485 and 535 nm TAMRA 535 and 595 nm PT14 405 and 450 nm. 4 = primary cleavage site confirmed by MS. AMC = aminomethylcoumarin. RhllO = rhodamine 110. yE = glutamic acid attached to RhllO via its carbonic acid in side chain. EDANS = fluorophore 5-[(2-aminoethyl)amino]naphthalene-l-sulphonic acid. DABCYL = 4-(4-dimethylaminophenylazo)benzoic acid quencher. BTN = biotin. PT14 = acridone-based fluorescence lifetime label. 

Given the inherent statistical nature of the discrete processes (such as photon absorption, secondary electron generation, PAG excitation, acid-quencher annihilation, deprotection, etc.) involved in advanced resist imaging, say, with EUV lithography, a credible concern has been reported that resists may reach a shot noise limit whereby low doses of high-energy EUV photons may cause the number of photons to fall to such low levels that the statistical variations inevitably will cause the LER to increase beyond an acceptable limit.This acceptable limit is referred to as the shot noise limit, and it is defined as the limit imposed by the statistical probability of underexposing a pixel. ... 

In a three-necked round bottom flask equipped with a pressure equahzer dropping fimnel fitted with a calcium chloride tube at the top, a mixture of 10 g (0.067 mol) ethyl orthoformate and 0.09 ml of BFa-ether complex was given to which 3 g (0.42 mol) vinylethylether was added dropwise during 15 min at a temperature below 45 °C. After the addition, the mixture was stirred constantly at 33 °C for 1 h. This was followed by the addition of 0.3 g sodium carbonate and the stirring was continued for an additional 3 h at room temperature. The precipitate was filtered and the filtrate was fi actionated in vacuum in the presence of a small quantity of sodium carbonate as an acid quencher to yield 2.5 g (85 %) 1,1,3,3-tetraethoxypropane, b.p. 90 °C at 800 Pa. The product was characterized by spectral data and elemental analysis. 

In the presence of acid quenchers like plasticizing additives and dissolution inhibitors, which may consume some of the generated acids (as shown in equation 4), the rate of acid depletion due to the quencher (Q) is given by equation 5 ... 

It has been shown in Chapter 5, the fluorescence quenching of the DPA moiety by MV2 + is very efficient in an alkaline solution [60]. On the other hand, Delaire et al. [124] showed that the quenching in an acidic solution (pH 1.5-3.0) was less effective (kq = 2.5 x 109 M 1 s 1) i.e., it was slower than the diffusion-controlled limit. They interpreted this finding as due to the reduced accessibility of the quencher to the DPA group located in the hydrophobic domain of protonated PMA at acidic pH. An important observation is that, in a basic medium, laser excitation of the PMAvDPA-MV2 + system yielded no transient absorption. This implies that a rapid back ET occurs after very efficient fluorescence quenching. 

Fatty Acid Transporters. Figure 2 Quencher-based real-time fatty acid uptake assay with a fluorescently labeled FFA analogue (C1-Bodipy-C12). Predominantly protein-mediated fatty acid uptake by 3T3-L1 adipocytes (diamonds) was compared with diffusion-driven uptake by fibroblasts (squares) using the QBT Fatty Acid Uptake reagent (Molecular Devices Corp., CA, USA), which contains C1-Bodipy-C12 as substrate in conjunction with a cell impermeable quencher. Uptake kinetics was recorded using a Gemini fluorescence plate reader. Error bars indicate the standard deviations from 12 independent wells. RFU relative fluorescence units. 

Time-resolved luminescence quenching measurements using the probe Tb(pyridine-2,6-dicarboxylic acid)i and the quencher bromophenol blue show the existence of micellar clusters in AOT-based w/o microemulsions. The fast exchange appearing over several microseconds was attributed to intracluster quenching, whereas the slow exchange on the millisecond time scale was attributed to intercluster exchange [243]. 

Nihro, Y., Miyataka, H., Sudo, T., Matsumoto, H. and Satoh, T. (1991). 3-O-Alkylascorbic acids as free radical quenchers synthesis and inhibitory activity effect on lipid peroxidation. J. Med. Chem. 34, 2152-2157. 

At present, the relevance of these results to photode-gradationl 0f condensates 1 is a matter of speculation. Of particular interest is identification of the photoproduct quencher(s) (PP, Scheme I). Possible candidates are salicylic acid derivatives, which exhibit the requisite absorptivity at about 300 nm, and which may be formed by oxidation of ortho-photo-Fries products (Scheme III), as illustrated in eq. 1. 

Proteases are one of the largest families of enzymes and are involved in a multitude of vital processes. Due to their biological relevance and diversity, multiple fluorescent reporters monitoring their activity have been designed and successfully applied in vitro and in vivo [112-114]. Standard small molecule FRET probes for proteases consist of an amino acid sequence flanked by a FRET pair, consisting of two fluorophores or one fluorophore and a quencher molecule. Upon cleavage of the peptide sequence, the emission of the donor fluorophore is dequenched and the intensity increases whereas the emission of the acceptor decreases and vanishes more or less completely in those cases where the acceptor is fluorescent (see Fig. 6.11). 

Another important group of hydrolytic enzymes are phospho- and cyclophosphodiesterases. They catalyze the hydrolysis of phospho-diester bonds and many of the most relevant biological substrates are nucleic acids. Phospholipase C and D are also important examples. Initial attempts to measure phosphodiesterase activity placed a phosphodiester between a fluorophore and a quencher and the probe was tested in vitro [146], This system was slightly modified by Caturla and used for the identification of catalysts with phosphodiesterase activity [147], More recently, Nagano and co-workers used a coumarin donor and fluorescein as a FRET... 

Rate measurements are straightforward if the carbenes can be monitored directly. As a rule, the decay of carbene absorption is (pseudo) first-order, due to rearrangement and/or reaction with the solvent. In the presence of a quencher, the decay is accelerated (Eq. 1), and the rate constant kq is obtained from a plot of k0bs versus [Q], Curved plots were often observed with proton donors (HX) as quenchers, particularly for high concentrations of weakly acidic alcohols. Although these effects have been attributed to oligomerization of the alcohols,91 the interpretation of curved plots remains a matter of dispute.76 Therefore, the rate constants reported in Tables 2-4 are taken from linear (regions of) obs-HX plots, or refer to a specified concentration of HX. 

If the reaction rates of a specific carbene with various quenchers are studied in the same solvent, and with small concentrations of Q, K will be constant. Relative reactivities for the singlet state of a spin-equilibrated carbene can thus be derived. However, few researchers have varied the acidity of ROH, estimated kinetic isotope effects, and compared alcohols with ethers (Table 4). The data indicate proton transfer to diarylcarbenes (139d, 139k, 205, 206)112-117 and diadamantylcarbene (207).118... 

Three C60 derivatives with two to four malonic acid groups (DMA C60, TMA C60, and QMA C60) were prepared and the phototoxicity of these compounds against HeLa cells was determined by MTT assay and cell cycle analysis (Yang et al., 2002). The relative phototoxicity of these compounds was DMA C60 > TMA C60 > QMA C60. Hydroxyl radical quencher mannitol (lOmM) was not able to prevent cells from the damage induced by irradiated DMA C60. DMA C60, together with irradiation, was found to decrease the number of G(l) cells from 63% to 42% and increase G(2) + M cells from 6% to 26%. 

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