Hyperchromic shifts

The UV-Vis spectra of the noncoordinated 5-amino-37/-l,3,4-thiadiazole-2-thione 26 and its organotin(iv) complex exhibit two absorption bands at 256 and 318 nm assigned to the 7t-7t and n-jt transitions of the C=N chromophore, respectively <2006SAA148>. These bands undergo a hyperchromic shift upon complexation supporting the participation of the C=N group in the coordination. 

Figure 24 shows the bathochromic and hyperchromic shifts of the of DNA on addition of increasing rj quantities of NjPjAzg to the medium. These effects... 

N3PjA2 and N P AZg, which exhibit significant activity against either L1210 and P388 leukemias or B16 melanoma, induce a noticeable fluorescence decrease and bathochromic and hyperchromic shifts ... 

The chromophore of phenylephrine is not extended but its structure includes a phenolic hydroxyl group. The phenolic group functions as an auxochrome under both acidic and alkaline conditions. Under acidic conditions it has two lone pairs of electrons, which can interact with the benzene ring and under basic conditions it has three. Figure 4.11 shows the bathochromic and hyperchromic shift in the spectrum of phenylephrine, which occurs when 0.1 M NaOH is used as a solvent instead of 0.1 M HCl. Under acidic conditions the X max is at 273 and has an A (1 %, 1 cm) value of 110 and under alkaline conditions the X max is a 292 nm and has an A (1%, 1 cm) value of 182. 

The following equation can be used for an acid (for a base the log term is subtracted) where increasing pH produces a bathochromic/hyperchromic shift ... 

It is well known that anthocyanins with hydroxyl groups in orr/zo-position to each other form complexes with aluminum ion leading to bathochromic and hyperchromic shifts in their absorption spectra. Complexation of AF" " with synthetic and natural anthocyanins has been investigated in aqueous solutions within the pH range 2 to 5. As shown by UV-vis... 

The middle phase, which is characterized by a hyperchromic shift and the formation of acid-soluble oligonucleotides monoesterified phosphate can be detected. In this phase, the increase of ultraviolet absorption and of acid-soluble oligonucleotides is linear with the reciprocal... 

The terminal phase, which shows an increasingly slower, further increase in the hyperchromic shift and acid-soluble oligonucleotide formation. Both phenomena, however, are no more linear with number of... 

These have generally been investigated by hyperchromic shift or acid solubility assays and therefore bear on the middle phase of the DNA degradation. 

Mercaptans (R-SH) [35] are weak acids (pKa around 10) and give rise to an equilibrium in aqueous solution. In basic media, bathochromic and hyperchromic shifts are observed in all cases. This effect is particularly marked with thiophenate ion because of a stabilisation of the negative charge with the n electrons of the aromatic ring. By adjusting the pH of sample to 11 after addition of sodium hydroxide solution 2.5 M, the spectra show a well-defined peak of absorbance at 238 nm for the alkylthiols or 263 nm for the thio-phenols. The application of the deconvolution method allows the estimation of the global concentration of mercaptans in wastewater. 

The bathochromic and hyperchromic shifts of n—mi or ti—mi absorbances (Figure 17.5) of the aryl rings caused by the introduction of two alkoxy groups correlated well with the increased photolability of nitroveratryl linkers during 365 nm irradiation. 

Figure 17.5 Bathochromic and hyperchromic shifts of n-Mt orTt-Mt absorbances of nitrobenzyl-derived photolabile linkers 13 (—) 14 ( ) 15 (- ), and phenacyl (—).

The melting of DNA can be easily monitored by a hyperchromic shift resulting from the unstacking of base bases and dissociation of the duplex DNA. This quick and simple method can also be applied to quadruplex DNA utilizing the same principles. Measuring the spectral absorbance at 295 nm, a maximum for... 

Substitution on the benzene ring can cause bathochromic and hyperchromic shifts. Unfortunately, these shifts are difficult to predict. Consequently, it is impossible to formulate empirical rules to predict the spectra of aromatic substances as was done for dienes, enones, and the other classes of compounds discussed earlier in this chapter. You may gain a qualitative understanding of the effects of substitution by classifying substituents into groups. 

The stability of dsDNA can be determined through a temperature denaturation study. Native dsDNA will denature to ssDNA as the temperature of the solution is increased. This is a reversible process, and the ssDNA will anneal to dsDNA on slowly cooling the denatured solution. This behavior can be followed spectroscopically (Fig. 6.11) by noting the increase in A260nm temperature, indicating the hyperchromic shift as the dsDNA denatures to ssDNA. The... 

Fig. 6.10. Hyperchromic shift between doubie-stranded and singie-stranded DMA. Singie-stranded DNA has a higher uitravioiet absorbance at 260 nm than does doubie-stranded DNA.

Fig. 6.11. Stability of double-stranded DNA (dsDNA) based on the GC content of the nucleic acid. The melting temperature is detected by a hyperchromic shift that occurs during the temperature-induced melting of dsDNA to single-stranded DNA and is shown to increase as the GC content of dsDNA increases.

We have used cesium chloride density gradient centrifugation to clean up phaiol-chloroform extracted, ethanol precipitated DNA and measured the "hyperchromic shift" when dsDNA denatures to ssDNA as an indication of DNA purity. A "hyperchromic shift" of more than 40% indicates that the DNA is of sufficient purity for quantitative hybridization. 

The strain energies in the twisted polyarenes have been determined by comparison of heats of combustion with those of the corresponding nonstrained isomers. In the case of 4,5-dimethylphenanthrene, the comparison was with that of 2,7-dimethylphenanthrene [15]. The bathochromic and hyperchromic shifts of the UV spectra of twisted arenes have been used to detect the presence of twisted distortion [16]. 

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