Tannic acids structure

Structural Formula A complex of amphetamine, C HsCHjCHlCHsiNHj and tannic acid Chemical Abstracts Registry No. 1407-85-8... 

To elucidate some enzymatic characteristics of the isolated laccases I, II, and III, substrate specificities for several simple phenols, electrophoresis patterns, ultraviolet spectra, electron spin resonance spectra, copper content, and immunological similarities were investigated. Tyrosine, tannic acid, g c acid, hydroquinone, catechol, pyrogallol, p-cresol, homocatechol, a-naphthol, -naphthol, p-phenylenediamine, and p-benzoquinone as substrates. No differences in the specificities of these substrates was found. The UV spectra for the laccases under stucfy are shown in Figure 4. Laccase III displays three adsorption bands (280, 405, and 600nm), laccase II shows one band 280nm), and laccase I shows two bands (280 and 405 nm). These data appear to indicate differences in chemical structure. The results of the copper content analysis (10) and two-dimensional electrophoresis also indicate that these fractions are completely different proteins (10), Therefore, we may expect differences in substrate specificities between the three laccase fractions for more lignin-like substrates, yet no difference for some simple phenolic substrates. 

The information in Table I reveals differences between sane of the inportant types of tannin. Tannic acid is unique for its occurrence in all reports of diet-induced gut lesion and gastrointestinal damage (vertebrate or invertebrate) it is also the only tannin for which metabolism and excretion are reported. By contrast condensed tannins are not thought to leave the gut lumen. Thus,in comparison with tannic acid condensed tannins would not be espected to drain 1-carbon metalx>lism, notably methionine resources. However, the reports by Elkin (] ) and Ford ( ) of corrective methionine treatment for chicks fed a condensed-tannin diet, indicate that sane condensed tannin may enter the body or that methionine can react with tannin in the gut, so perhaps the position is once again not clear cut on tannin structure and its impact on methionine levels. The conclusion can, however, be made that despite its hydrolyzability, tannic acid does exert an allelochemical effect which is not abolished by hydrolysis. 

Many medium resolution structures of macromolecular assemblies (e.g., ribosomes), spherical and helical viruses, and larger protein molecules have now been determined by electron cryomicroscopy in ice. Four atomic resolution structures have been obtained by electron cryomicroscopy of thin 2D crystals embedded in glucose, trehalose, or tannic acid (11-14), where specimen cooling reduced the effect of radiation damage. One of these, the structure of bacteriorhodopsin (1 l)provided the first structure of a seven-helix membrane protein. The medium resolution density distributions can often be interpreted in terms of the chemistry of the structure if a high resolution model of one or more of the component pieces has already been obtained by X-ray, electron microscopy, or NMR methods. As a result, the use of electron microscopy is becoming a powerful technique for which, in some cases, no alternative approach is possible. Useful reviews [e.g., Dubochet et al. (9), Amos et al. (15), Walz and Grigorieff (16), and Baker et al. (17)] and a book [Frank (18)] have been written. 

One of the oldest known methods of producing wash-fast colors involves the use of metallic hydroxides, which form a link, or mordant (L. mordere, to bite), between the fabric and the dye. Other substances, such as tannic acid, also function as mordants. The color of the final product depends on both the dye used and the mordant. For instance, the dye Turkey Red (alizarin) is red with an aluminum mordant, violet with an iron mordant, and brownish-red with a chromium mordant. Some important mordant dyes possess a structure based on triphenylmethane, as do Crystal Violet and Malachite Green. 

Contradictory opinions have been referred to in the literature particularly on the nature of the iron-tannate and its interaction with the rusted steel due to the diversity of the material used in different studies. Studies have included the use of tannic acid [7-10], gallic acid [11], oak tannin [12, 13], pine tannin [14] and mimosa tannin [15]. In order to establish the correlation between the ferric-tannate formation and the low inhibition efficiency observed at high pH from the electrochemical studies, phase transformations of pre-rusted steels in the presence of tannins were evaluated. In this work the quantum chemical calculations are conducted to analyse the relationship between the molecular structure and properties of ferric-tannate complex and its inhibitory mechanism. 

Khan NS, Hadi SM (1998) Structural features of tannic acid important for DNA degradation in the presence of Cu(n). Mutagenesis 13 271—274... 

Note Composition of the fix buffer is critical to preservation of some structures. The buffer used here is optimized for the preservation of membrane structures (Allan and Vale, 1994). Tannic acid improves preservation of protein structures such as the NPC (Goldberg, Blow, and Allen, 1992), but causes vesicularization of ER tubules. 

These compounds contain hydroxyl groups. Therefore, they may act as an electron donor. The macromolecular structure of these compounds (especially of tannic acid) allows for effective stabilization of the size of resulting nanoparticies. 

Fig. 9. Typical structural units in the tannic acid molecule...

To preserve beer colloidal stability, brewers usually remove haze-active materials [34]. To get rid of haze-active proteins, precipitation with tannic acid, hydrolysis with papain and adsorption to bentonite [35] or silica gel [36, 37] are very effective, but unfortunately in some cases, such procedures also remove foam proteins. To remove haze-active polyphenols, the most usual way is adsorption to polyvinylpolypyrrolidone-PVPP. Because of the structural analogy between these compounds and proline [38], pyrrolidone rings bind polymerized flavanoids through hydrogen and ionic bonds. 

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