Bound form

Figure 7-15 shows the time evolution of the temperature, total energy, and potential energy for a 300 ps simulation of the tetracycline repressor dimer in its induced (i.e., hgand-bound) form. Starting from the X-ray structure of the monomer in a complex with one molecule of tetracycline and a magnesium ion (protein database... 

Nicotinamide and nicotinic acid occur in nature almost exclusively in the bound form. In plants, nicotinic acid is prevalent whereas in animals nicotinamide is the predominant form. This nicotinamide is exclusively in the form of NAD and NADP. 

Nicotinic acid is found in plants associated with both peptides and polysaccharides. For example in wheat bran, two forms are described a peptide with a molecular weight of approximately 12,000 and a carbohydrate complex that is called niacytin. Polysaccharides isolated from wheat bran have been found to contain 1.05% nicotinic acid in bound form. Hydrolysis yielded a fragment identified as P-3-O-nicotinoyl-D-glucose (25). 

From a bioavailabihty standpoint, the fact that a significant amount of nicotinic acid is in a bound form has important biological consequences. Poor bioavailabihty stems from the fact that the ester linkage is resistance to digestive enzymes. In the case of com, this condition can be alleviated if com is pretreated with alkah. This food preparation method is frequently practiced in Mexico for the preparation of tortillas. 

Phenyl-2-propen-l-ol [104-54-1], commonly referred to as cinnamyl alcohol, is a colorless crystalline soHd with a sweet balsamic odor that is reminiscent of hyacinth. Its occurrence in nature is widespread as, for example, in Hyacinth absolute (Hyacinthus orientalis) (42), the leaf and bark oils of cinnamon Cinnamomum cassia, Cinnamomum lancium, etc), and Guava fmit [Psidiumguajava L.) (43). In many cases it is also encountered as the ester or in a bound form as the glucoside. 

Figure 13.8 Interactions involved in the switch from the inactive GDP- (blue) to the active GTP- (green) bound forms of G from transducin. The diagram illustrates the local changes required in the switch I and II regions in order to bring the side chain of Thr 177 and the main chain N of Gly 199 into contact with the 7 phosphate of GTP. (Adapted from D. Lambright et al., Nature 369 621-628, 1994.)...

Most commercial cast irons contain 2.5-4% carbon, and it is the occurrence of some of this carbon as free graphite in the matrix that is the characteristic feature of thin material. About 0.8-0.9% carbon is in a bound form as cementite (iron carbide). 

Fig. 2.1 Mechanism of the bacterial bioluminescence reaction. The molecule of FMNH2 is deprotonated at N1 when bound to a luciferase molecule, which is then readily peroxidized at C4a to form Intermediate A. Intermediate A reacts with a fatty aldehyde (such as dodecanal and tetradecanal) to form Intermediate B. Intermediate B decomposes and yields the excited state of 4a-hydroxyflavin (Intermediate C) and a fatty acid. Light (Amax 490 nm) is emitted when the excited state of C falls to the ground state. The ground state C decomposes into FMN plus H2O. All the intermediates (A, B, and C) are luciferase-bound forms. The FMN formed can be reduced to FMNH2 in the presence of FMN reductase and NADH.

In tissues, most coelenterazine exists in a protein-bound stabilized form, which liberates free coelenterazine when extracted with methanol. Thus, the amount of coelenterazine measured by this method is the sum of free coelenterazine and its protein-bound form. 

Two types of stabilized coelenterazine are known to exist in biolu-minescent organisms, i.e. the protein-bound form (usually bound to a calcium-binding protein) and the enol ester form (usually enol-sulfate see Structure I, Fig. 5.5). 

The assay result of coelenterazine described in Section C5.1 includes the amount of the protein-bound form of coelenterazine in addition to free coelenterazine. The assay of only the protein-bound form, or only the free coelenterazine, is complicated because the protein-bound form tends to liberate free coelenterazine by various stimuli, not only by Ca2+. An example of the measurement of protein-bound coelenterazine is given by Shimomura and Johnson (1979b). 

Although there is substantial homology among the membrane-bound forms of the mammalian adenylyl cyclases, the striking differences in the character and... 

Biotin can be synthesized by the human colon flora. The question to which extent this production contributes to covering the host-organism s requirements is, however, subject to discussion. In most foods of animal origin as well as in cereals, biotin prevails in the protein (= enzyme)-bound form as e-N-biotinyl-L-lysine (= biocytin). Brewer s yeast, liver, soya beans, and peanuts number among the biotin rich foods [1]. 

Since plasmin in free form (not bound to fibrin) is extremely and rapidly inactivated by the inhibitor system (Fig. 4), plasminogen activators are used for treatment of thrombosis. Under such a condition, if plasmin is formed by the activators (especially by tPA) at the site of fibrin, the bound form can degrade fibrin because it is protected against the inhibitor system. In the medical practice, mainly two endogenous plasminogen activators, tPA and uPA, and one exogenous, the streptokinase (SK) are used [1,4]. 

Thyroxine (3, 5, 3,5-L-teraiodothyronine, T4) is a thyroid hormone, which is transformed in peripheral tissues by the enzyme 5 -monodeiodinase to triiodothyronine. T4 is 3-8 times less active than triiodothyronine. T4 circulates in plasma bound to plasma proteins (T4-binding globulin, T4-binding prealbumin and albumin). It is effective in its free non-protein-bound form, which accounts for less than 1%. Its half-life is about 190 h. 

Triiodothyronine (3, 5,3-L-triiodothyronine, T3) is a thyroid hormone. It is producedby outer ring deiodination of thyroxine (T4) in peripheral tissues. The biologic activity of T3 is 3-8 times higher than that of T4. T3 is 99.7% protein-bound and is effective in its free non-protein-bound form. The half-life of triiodothyronine is about 19 h. The daily tur nover of T3 is 75%. Triiodothyronine acts via nuclear receptor binding with subsequent induction of protein synthesis. Effects of thyroid hormones are apparent in almost all organ systems. They include effects on the basal metabolic rate and the metabolisms of proteins, lipids and carbohydrates. 

Pugach P, Marozsan AJ, Ketas TJ, Landes EL, Moore JP, Kuhmann SE (2007) HIV-1 clones resistant to a small molecule CCR5 inhibitor use the inhibitor-bound form of CCR5 for entry. Virology 361 212-228... 

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