Commercially Available Substrates

Some commercial substrates were/are also available for SERS but to date none of them have become universal substrates for SERS analytical applications. Klarite substrates designed from silicon regular inverse pyramidal patterns coated with Au layer (Pemey et al. 2007) are one example. This substrate had been commercially available initially by a spin-off enterprise of the University of Southampton and then marketed by the Renishaw, Inc., Renishaw Diagnostics. Although the Klarite substrates do not provide high EF, the spectral reproducibility is sufhcient for some sensing applications. 

3 Basics of Surface-Enhanced Raman Scattering (SERS) 

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The diastase activity was traditionally determined according to the Schade method in the earlier years (Schade et al., 1958). One unit of diastase activity (or more specifically, a-amylase), DN, is defined as that amoimt of enz)nne that converts 0.01 g of starch to the prescribed endpoint in 1 h at 37 °C under the experimental conditions. In this assay, a standard solution of starch, which reacts with iodine to produce a color solution, is used as a substrate for honey enzymes under the standard conditions (Rendleman, 2003). A recently developed procedure uses an insoluble, dyed starch substrate (Persano Oddo and Pulcini, 1999). As this substrate is hydrolyzed by ot-amylase, soluble dyed starch fragments are released into solution. After reaction termination and insoluble substrate removal by centrifugation, absorbance of the supernatant solution (at 620 nm) is measured. The absorbance is proportional to the diastase activity. This procedure has been widely adopted in the honey industry due to the convenience of a commercially available substrate and the simple assay format. 

Add the commercially available substrate solution containing 5-Bromo-4-chloro-3-indolyl Phosphate (BCIP)/Nitroblue Tetrazolium (NBT) (SIGMA) to the blot till it is just submerged. 

Another commonly used way to detect caspase activity is by enzyme assay that measures the cleavage of synthetic substrates on their incubation with lysates of apoptotic cells [83]. Commercially available substrates are conjugated either to the chromophore or to a fluorochrome. On cleavage of the substrate, the liberated chromophore/fluorochrome is spectrofotometrically/ fluorometrically detected. 

While the ink droplet spreads up to 105 jtrm when no heat is supplied to the substrate, spreading is very hmited once the substrate is heated — the droplet viscosity increases and the spreading is limited accordingly. Most wide format printers, aimed to print on a variety of commercially available substrates, are using the "heated substrate" technology on flat-bed printers as well as on drum or roll printers. 

At the molecular level, portions of cellulose assume a highly structured crystalline form, while other parts are amorphous. Amorphous cellulose is more easily digested by enzymes than the crystalline parts. The fraction of crystalline cellulose is called the relative crystallinity, an index of digestibility. The crystallinity of commercially available substrates lies between 85 and 90%. Even so-called non-crystalline cellulose has a relative crystallinity of 65%. 

Methylcinnarnic acid (MCA) is a commercially available substrate for which the product ee was only 14% under the original conditions [86], and remained low (23%) after some improvement many years later [94]. However, the application of hydrogen-treated Pd/C under optimized conditions for PCA brought about a notable improvement in the hydrogenation of MCA that resulted in a 46% ee (Scheme 10.13) [100]. The product ee-value was higher with a bulkier a-substituent, while with a P-p-methoxyphenyl group the product ee was 86%. As... 

Stop Solution Once the enzymatic reaction has progressed to the desired extent, the activity of the enzyme should be stopped so that the color intensity of the reaction mixture remains within the quantification range of the plate reader. This can be achieved by acidifying the reaction mixture with a dilute solution of sulfuric or hydrochloric acid, or by the addition of commercially available substrate-specific stop solutions. 

Fig. 10.17 Picture showing how SP76 modular surface-mount components are attached to one of the commercially available substrates.

The aza Diels-Alder reactions of a, ff-unsaturated sulfinimines (140) represent a very efficient approach to enantiopure dihydro- and tetrahydropyridines (141) (Scheme 8.34, Table 8.11) for a reasonable reaction rate the 1-aza-l,3-butadiene moiety 140 must carry an electron-withdrawing group at the 3-position [65]. The compounds are accessible in only three steps starting from commercially available substrates. Thus, the enantiopure 1-aza-l,3-butadiene can be prepared from the enantiopure menthyl sulfinate with lithium hexamethyldisilazide followed by addition of acetic acid and an a, -unsaturated aldehyde. The cycloadditions of sulfinimines such as 140 run under mild conditions with high yields and excellent endo-selectivity in most cases when high pressure is applied. In these reactions two endo and two exo transition structures namely syn and anti to the sulfoxide moiety should be discussed. The cycloaddition of 140 and t-butyl vinyl ether was performed under various pressures ranging from 0.2 to 1.2 GPa. 

Sensitivity of a test in which a commercially available substrate, Phadebas , was used for the assay of a-amylase in sprouted wheat has been increased by the use of optimally buffered (pH 6.20) Cibacron Blue dyed amylose at 60 With the modified test, measurable a-amylase levels were in the range of 3-30 millidextrinizing units (mDU) as compared to the 10-90 mDU range in a test previously reported for bread wheats. The modification extends the use of the test to evaluation of sprout damage in wheats used in the manufacture of Japanese noodles and sponge cakes. 

There have been several in vitro assay methods reported recently that are based on spectrophotometric, fluorometric, or amperometric means of detection. These assays were investigated using various natural, commercially available substrates or from specially designed and synthesized probes. The prerequisite for the donor substrate is a ketol moiety, and for the acceptor substrate an aldehyde function. 

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