Ultraviolet absorption spectra, for

The pA a shift can be directly measured by the solvatochromic shift of the ultraviolet absorption spectra. For PCP, the p%lir is 5.97 in phosphatidyl choline membranes, and increases up to 6.78 in the negatively charged phosphatidyl glycerol membranes [123], The addition of cholesterol decreases the pATam again slightly in both types of membranes. 

Visible and near-ultraviolet absorption spectra for aqueous solutions of Co(NH3)63+ and Co(NH3)5Br2+ are shown in Figure 6. The spectrum of Co(NH3)83 + is typical of diamagnetic, octahedral d6 systems, consisting of two broad bands of low intensity centered near 500 mjx and near 350 m and a very intense band in the ultraviolet. In the Co(NH3)5Br2+ spectrum the high-intensity bands occur at sig-... 

The ultraviolet absorption spectra for lomefloxacin were obtained on a Hewlett Packard 8451A Diode Array Spectrophotometer as a function of pH. The lomefloxacin solutions were prepared in 0.15 M acetate buffer, 0.05 M phosphate buffer, and 0.15 M borate buffer ( i = 0.15 M with NaCl) at pH 5,7, and 9, respectively. These spectra are given in Figure 13. The molar absorptivities (a) and absorption maxima as a function of pH are summarized in Table 3. 

Dehydrogenase Reactions. The reduced (NADH) and oxidized (NAD+) forms of nicotinamide adenine dinucleotide exhibit marked differences in their ultraviolet absorption spectra and are, therefore, widely used for following the course of dehydrogenase reactions. The ultraviolet absorption spectra for NAD" " and NADH are given in Figure 22.4. NAD has negligible absorption at 340 nm while NADH has an absorption maximum, and so it is a simple matter to monitor the increase or decrease in NADH concentration. 

FIGURE 14-1 Ultraviolet absorption spectra for 1.2,4,5-tetrazine. In (a), the spectrum is shown in the gas phase, where many lines due to elecirontc. vibrational, and rotational transitions can be seen. In a nonpolar solvent (b). the electronic transitions can be observed, but the vibrational and rotational structure has been lost. In a polar solvent (c), the strong intermolecular forces cause the electronic peaks to blend, giving only a single smooth absorption band. (From S. F. Mason, J. Chem. Soc., 1959.1265.)... 

Figure 3 Ultraviolet absorption spectra for various concentration of a solution of BTZ-2 (1.0-cm cell in cyclohexane). 

Figure 3. Ultraviolet Absorption Spectra for 3.5 micrometer thick film of PMDA/ODA based poly(amic ethyl ester).

The ultraviolet absorption spectra of most new thiazoles currently synthesized have been described and occasionally used for structural... 

The 9ai7-quinolizine structure (82) for the labile adduct from 3,5-dimethylpyridine was clearly established by the nuclear magnetic resonance studies of Richards and Higham, and subsequent work showed the labile adduct from 3-methylpyridine was analogous. As the labile adducts from all the pyridines and benzopyridines so far examined have very similar infrared absorption spectra in the 5-7 yn. (carbonyl and aromatic) region and within quite close limits very similar ultraviolet absorption spectra, it can be concluded that all are derivatives of 9aH-quinolizine,... 

The ultraviolet absorption spectra of the anhydro-bases in acid solution or in protic solvents are those of the 3,4-dihydro-)3-carbolinium ion (Ajnax 355 mp, for 438b and 438c). In alkaline solution and in nonionizing solvents absorption at a shorter wavelength (A ax 315 m/x) is observed. In general, solutions of the anhydro-bases in acid and in protic solvents are more deeply colored than their solutions in basic or in non-ionizing media. 

Ultraviolet absorption spectra of tetrahy dro-1,3-oxazines do not show any maximum. Only after the introduction of a chromophoric group do bands appear. Thus 5-nitro derivatives show a strong maximum near 270 m/A, which is typical for a nitro group, and another one near 200 m(x which is probably also produced by the nitro group.In the instance of 5-nitro-5-hydroxymethyl derivatives, the absorption is much weakened this was explained by Urbanski in terms of a hydrogen bond between the hydroxyl and the nitro group. Other chromophores, such as C=0, C=NH, C—C, also cause the appearance of absorption maxima in the range 210-265 m/A and near 360... 

Visible and ultraviolet absorption spectra are measured in an absorption spectrometer. The source gives out intense visible light or ultraviolet radiation. The wavelengths can be selected with a glass prism for visible light and with a quartz prism or a diffraction grating for ultraviolet radiation (which is absorbed by glass). A typical absorption spectrum, that of... 

Ultraviolet absorption spectra were obtained from a Cary 118C Spectrophotometer. Luminescence measurements were obtained from a Perkin-Elmer Model MPF-3 Fluorescence Spectrophotometer equipped with Corrected Spectra, Phosphorescence and Front Surface Accessories. A Tektronix Model 510N Storage Oscilloscope was used for luminescence lifetime measurements. Fiber irradiation photolyses were carried out in a Rayonet Type RS Model RPR-208 Preparative Photochemical Reactor equipped with a MGR-100 Merry-go-Round assembly. 

The ultraviolet absorption spectra of the methylated bagasse native lignins are represented in Fig. 4. Once again absorption at 282 mp. has been magnified relative to that in the region above 300 mp. Furthermore, the completely methylated lignin exhibits an absorption maximum at 310 mp, rather than at 315 mp. It is significant that these spectra are similar to those obtained by Patterson and Hibbert for the 3.4-dimethoxyphenyl-l-propanone compounds (S3). 

Merocyanine Dye Method for Acid Analysis. Resist photochemistry can often be monitored by the changes in ultraviolet absorption spectra associated with a bleaching of the sensitizer absorbance. In the case of resist systems with triphenylsulfonium salts, no change in the film absorption is observed on irradiation. In order to determine the amount of acid produced, a direct method for acid analysis was required. A highly sensitive method was desirable since the amount of acid produced is approximately 10 6 mmol for a 1 micrometer thick film on a 2 inch wafer. Furthermore a nonaqueous technique is preferred in order to avoid hydrolysis of the hexafiuoroantimonate salt. Hydrolysis gives hydrogen fluoride (14) which makes accurate acid determination more difficult. 

Kratschmer W, Fostiropoulos K, Huffman DR (1990) The infrared and ultraviolet absorption spectra of laboratory-produced carbon dust evidence for the presence of the Cgo molecule. Chem Phys Lett 170 167-170... 

The ultraviolet absorption spectra of benzoic in 96 % ethanol (concentration = 8.3 ppm) and in 0.01 N HCl (concentration = 8.2 ppm) were recorded on a Shimadzu UV-265 spectrophotometer, and are shown in Figure 4. The spectra were not found to be greatly affected by the nature of the solvent used. An absorbance maximum of 227 nm was noted for the 96 % ethanolic solution, while a maximum at 229 nm was found in the 0.01 N HCl solvent. The absorbencies within these two solutions were found to be 0.815 and 0.768, respectively, so that the respective molar absorptivities are computed to be 12000 and 11400 liter/cm mole. 

In principle, absorption spectroscopy techniques can be used to characterize radicals. The key issues are the sensitivity of the method, the concentrations of radicals that are produced, and the molar absorptivities of the radicals. High-energy electron beams in pulse radiolysis and ultraviolet-visible (UV-vis) light from lasers can produce relatively high radical concentrations in the 1-10 x 10 M range, and UV-vis spectroscopy is possible with sensitive photomultipliers. A compilation of absorption spectra for radicals contains many examples. Infrared (IR) spectroscopy can be used for select cases, such as carbonyl-containing radicals, but it is less useful than UV-vis spectroscopy. Time-resolved absorption spectroscopy is used for direct kinetic smdies. Dynamic ESR spectroscopy also can be employed for kinetic studies, and this was the most important kinetic method available for reactions... 

Figure 1. Ultraviolet absorption spectra of Marlex-5003 polyethylene irradiated to 421 Mrad at liquid nitrogen temperature in vacuo. Curve 1 spectrum taken at liquid nitrogen temperature (Int) after irradiation. Curve 2 spectrum taken at room temperature immediately after warming to room temperature (rt). Curve 4 spectrum taken at rt after standing for 46 hours at rt in vacuo. Curve 3 spectrum taken at Int after the 46 hours at rt...

Figure 2. Ultraviolet absorption spectra of Mar-lex-5003 polyethylene all taken at liquid nitrogen temperature (Int). Irradiation at Int for 20 minutes in an electron beam. Curve 1 after 16 hours storage at room temperature in vacuo.

A coordination number of 7 does not seem likely for chromium (III) also, the infrared spectrum indicates that this compound contains uncoordinated hydroxyl groups. The similarity of the visible-ultraviolet absorption spectra of [Cr(HO-A)2] and [Cr(AcO-A)2] (above) is further evidence of the identical character of the donor groups in both compounds, and hence, hydroxyl groups appear to be uncoordinated in the former. We must seek an explanation not involving coordination of the hydroxyl oxygen to chromium (III). 

Values of the dissociation constant due to N in the ring of nicotinic acid and the amide were found to be 3.55 x 10-11 and 2.24 x 10 n (from ultraviolet absorption spectra), whereas the value for the dissociation of amide groups is generally much smaller (acetamide, 3.1 x 10"15). It is, therefore, reasonable to assume that Kt and K4 are large compared with K2 and K3. Using these assumptions, the observed rate, v, is given by... 

Figure 5-5 Near ultraviolet absorption spectra of cytidine, uridine, adenosine, and guanosine. 1. Monoprotonated form of cytidine (for which pKa = 4.2). 2. Neutral form (pH 7) of cytidine. 3. Neutral form of uridine (for which pKa = 9.2). 4. Monoanionic form of uridine. 5. Monoprotonated form of adenosine (pKa = 3.5). 6. Neutral form of adenosine. 7. Neutral form of guanosine (pKa = 9.2). 8. Monoanion of guanosine.

Ultraviolet absorption spectra have been published for enzymes from the following sources calf intestine (90), horse kidney (69a), and human placenta (28). For crystalline placental phosphatase E]%"s nm = 7.8 (in 0.05 M phosphate buffer pH 7.0). Titration curves for calf intestinal phosphatase (range pH 4-10) indicate an isoelectric point of 5.7 which is invariant with respect to temperature (15°-25°) and ionic strength (0.02-0.5) (91). 

Although the diagram does not give a quantitative interpretation of the heat-bodying phenomena of linseed oil it allows an easy comparison of the conjugation and polymerization reactions under different conditions. Chemical and physical analytical methods for the determination of conjugated double bonds (diene value, ultraviolet absorption spectra) confirmed the conclusions about the conjugation phenomena. 

The ultraviolet absorption spectra of most 1-hydroxy-, 1-acyloxy-, and 1-alkoxyindoles are quite similar to those of the corresponding indoles representative examples are listed in Table 11. In general, they show a small shift towards the visible, and this is accentuated in the 1-hydroxyindoles on the addition of alkali when the proton can be removed. The UV spectrum reported (67BSF1296) for 1-hydroxyindole is certainly that of a polymer, for it shows no absorption at —280 nm, which is characteristic of these compounds and of 2,3,3-trimethyl-3//-indolenine 1-oxide, a model for the 3//-tautomer (Table II). 

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