Biological activity ionization

Specific biological activity of carboxylic acids peroxide derivatives in compaiison with their oxidation ability and ionization degree in aqueous solutions has been considered. Peroxyoctanoic, diperoxynonandioic and diperoxydecandioic acids give the most intense bactericidal effect among researched cai boxylic acids peroxide derivatives. The perspectives of use of the aliphatic middle-chain peracid C8-C9 as anti-infective agents have been discussed. 

Benzo[a]pyrene, a molecule with five, fused, hexagonal rings, is among the most carcinogenic of the polycyclic aromatic hydrocarbons (PAHs). Such biological activity may be related to the electronic structure of benzo[a]pyrene and its metabolites. Ionization energies of these molecules therefore have been investigated with photoelectron spectroscopy [28]. 

The structure-selective, electron-capture detector (ECD) is the second aost widely used ionization detector [115-118]. It owes Buch of its popularity to its unsurpassed sensitivity to a wide range of toxic and biologically active coapounds. Consequently, it is widely used in trace analysis for the detemination of pesticides, herbicides and industrial chemicals in the... 

Comer, J. E. A., The acid test ionization and lipophilicity of drugs influence on biological activity, Chem. Britain 30, 983-986 (1994). 

The activity of many enzymes is pH-dependent because the enzyme may ionize in solution and the biological activity of unionized and ionized forms may be different. In this case, the rate of an enzyme-mediated reaction can be expected to depend on the acidity of the solution. If the enzyme can lose more than one proton as the pH increases (Figure 8.12), the rate of reaction as a function of pH may display a maximum if the forms of the enzyme in strongly acidic or strongly basic solution are inactive, but the intermediate, monoanion, is active. An example of this behavior is provided by fumarase (Figure 8.13). 

The effect of a biologically active compound is based on its ability to form a complex with a receptor. The intensity of the biological effect is proportional to the stability of this complex, which is dependent on the strength of the interaction of the effector molecule with the active centre of the receptor. The electron structure of the molecule can be decisive for this interaction and this may explain the correlation of ionization potentials and pharmacological properties of certain compounds. 

Several compounds have been investigated as modulators of me biological response to ionizing radiation. Two approaches have been pursued increase of me tolerance to ionizing radiation for normal tissues (radioprotectors), inaeased biological activity of radiation toward cancer cells (radiosensitizers). 

Aspirin is an ester, bnt it still contains a carboxylic acid fnnction (p/Ca 3.5). In aqueous solntion, there will thus be significant ionization. However, this ionization now provides an acid catalyst for ester hydrolysis and initiates autolysis (autohydrolysis). The hydrolysis product salicylic acid (pACa 3.0) is also acidic both aspirin and salicylic acid are aromatic acids and are rather stronger acids than aliphatic compounds such as acetic acid (pACa 4.8) (see Section 4.3.5). An aqueous solution of aspirin has a half-life of about 40 days at room temperature. In other words, after about 40 days, half of the material has been hydrolysed, and the biological activity will have deteriorated similarly. 

The success of API is due, at least in part, to the fact that both ion-spray and heated-nebulizer involve soft ionization processes that provide an abundance of molecular ions. This results in simple, easy-to-interpret spectra affording molecular weight information. Because of these features, this interface is perfectly suited to natural products chemistry. We use LC-MS on the material in those tubes identified as having biological activity. The combination of molecular weight and UV-visible data of biological active fractions is used for identification. 

The presence of hydroxyl groups in the polymer units allows to use this reactive site for covalent binding of compounds of interest, for instance biologically active compounds, whereas the presence of ionizable phosphate groups makes these polymers soluble in water. 

A2-1,3,4-Oxadiazolin-5-ones acylation, 6, 439 alkylation, 6, 439 biological activity, 6, 445 melting point, 6, 430 synthesis, 6, 441, 442 tautomerism, 6, 430 A3- l,3,4-Oxadiazolin-2-ones 5,5-disubstituted IR spectra, 6, 429 PE spectra, 6, 430 A3-1,3,4-Oxadiazolin-5-ones ionization potential, 6, 428... 

Alternative biosynthetic pathways can interconvert NAPE precursors into other anandamide-containing lipids whose biological activities remain unknown. We recently observed that the combination of soft ionization techniques such as... 

Because of a perceived importance of amino substituents for biological activities in 1,8-naphthyridines, e.g.,359 422 478 526 1395,1410 sucjj derivatives have been widely investigated, for example, with respect to their ionization,1043 NMR spectra,174 mass spectra, fluorescence properties, tautomerism, and conversion into cyanine-type dyes.768... 

Youngquist RS, Fuentes GR, Lacey MP, Keough T, Matrix-assisted laser desorption ionization for rapid determination of the sequences of biologically active peptides isolated from support-bound combinatorial peptide libraries, Rapid Commun. Mass Spectrom., 8 77-81, 1994. 

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