Properties, 67 table sharing

Cements based on phytic add set more quickly than their glass polyalkenoate or dental silicate cement cormterparts, but have similar mechanical properties (Table 8.2). They are unique among add-base cements in being impervious to acid attack at pH = 2-7. Unfortunately, they share with the dental silicate cement the disadvantage of not adhering to dentine. They do bond to enamel but this is by micromechanical attachment - the cement etches enamel - and not by molecular bonding. Lack of adhesive property is a grave weakness in a modern dental or bone... 

Chemical Family a group of elements that share similar chemical properties and share the same column in the periodic table, for example, halogens, alkali earth Chirality condition that describes the handedness of a molecule or whether a molecule exists in forms that can be superimposed on each other Chlorofluorocarbons also called CFCs, compounds consisting of chorine, fluorine, and carbon that are responsible for stratospheric ozone destruction Coagulation precipitation or separation from a dispersed state Coefficient of Thermal Expansion measure of the rate at which a substance will expand when heated... 

Another series of inner anhydrides, namely that of the general formula X = S02, is found in the bottom row of the table the members are sulfenes, iV-sulfonylamines and sulfur trioxide, the inner anhydrides of, respectively, sulfonic, sulfamic and sulfuric acids. The analogy is again helpful one of the most conspicuous features of sulfur trioxide is its high reactivity toward water and other nucleophiles this property is shared by sulfenes and sulfonylamines7. 

While lectins are structurally diverse, it is possible to group many of them into distinct families of homologous proteins that share conunon structural properties (Table 10.6). 

As shown in Fig. 1, the enzyme catalyzes the reduction of ribonucleoside diphosphates (Fig. lA) by dithiothreitol (Fig. IB). K values for CDP and DTT are 70 x Af and 20 mAf, respectively. The requirement for a dithiol suggests that, as for other class II RNRs, such as the extensively studied enzyme from Lactobacillus leichmannii, the hydrogen donor is very likely to be a dithiol protein such as thioredoxin or glutaredoxin. However, there is still no experimental evidence that an archaeal thioredoxin operates as an electron source for RNRs. The enzyme also requires AdoCbl for which a value of 1 pAf has been obtained (Fig. 1C). Finally, the reaction has an optimal temperature of 80° (Fig. ID), with very little activity at 30°. How AdoCbl resists such a high temperature and how the enzyme controls Co-C bond homolysis required for catalysis in thermophilic AdoCbl-dependent enzymes is an intriguing question. These properties are shared by other isolated thermophilic class II RNRs (Table II). 

Boron nitride shows many similarities to carbon owing to its isoelectronic valence electron structure that is, both compounds possess an equal sum of eight valence electrons (4 -i- 4 in carbon 3 -r 5 in boron nitride) and an equal sum of (two) atoms each (C2 BN). Consequently, boron nitride shares with carbon a multiple of polymorphic modifications with very similar properties (Table 11.5). 

We found that in B 880-type complexes from eight different species of bacteria, the BChl environments are extremely similar. These environments insure the same sets of binding sites for the conjugated carbonyls (Table 2) and, probably, for the Mg atoms, as well as the same local permittivity seen by the dihydrophorbin rings. Hence, the B 880-type complexes of Rhodospiriltales, as defined by their biochemical and electronic absorption properties, also share nearly identical structures around their dweller BChls. 

Compounds available in the United States are Hsted in Table 1. Whereas they vary in degree, all of them share similar HabiUties of cardiovascular side effects, the potential for central nervous system (CNS) stimulation, the development of tolerance, and abuse potential. AH, with the exception of ma2indol, are derivatives of phenethylamine. The introduction of an oxygen atom on the -carbon of the side chain tends to reduce CNS stimulant properties without decreasing the anorectic activity. Following the Federal Controlled Dmg Act of 1970, dmgs were classified into one of five schedules according to medical utiUty and abuse potential. 

The most important aspect of Table 27.1 is that the 20 anino acids that occur in proteins share the common feature of being a-anino acids, and the differences fflnong them are in their side chains. Peptide bonds linking carboxyl and a-anino groups characterize the structure of proteins, but it is the side chains that are mainly responsible for theh properties. The side chains of the 20 commonly occuning amino acids encompass both large and small differences. The major differences between amino acid side chains concern ... 

The reason usually cited for the great similarity in the properties of the lanthanides is that they have similar electronic configurations in the outermost 6s and 5d orbitals. This occurs because, at this point in the periodic table, the added electrons begin to enter 4f orbitals which are fairly deep inside the atom. These orbitals are screened quite well from the outside by outer electrons, so changing the number of 4/electrons has almost no effect on the chemical properties of the atom. The added electrons do not become valence electrons in a chemical sense—neither are they readily shared nor are they readily removed. 

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