1 Clinical Enzymology

Conformation of uncomplexed polyether macrocycles. The structure of bis(2'-carboxy-1',3'-xylyl)-24-crown-6 at 113 K

“…Bond distances listed in Table 3 correlate well with those found at 113 K in BACR5 (Goldberg, 1976) and BAPCR5 (Goldberg & Rezmovitz, 1978), and at room temperature in other 2,6-disubstituted benzoic acids (Benghiat & Leiserowitz, 1972). A significant exception refers to dimensions of the carboxy group which is ideally disordered only in the present example.…”

“…As in related 2,6disubstituted benzoic acids the plane of the carboxyl group is rotated with respect to the plane of the phenyl ring. The angle of twist in the present structure is 52 °, compared to 59 ° in BACR5 (Goldberg, 1976), 57 ° in BAPCR5 (Goldberg & Rezmovitz, 1978), 53 ° in 2,6dimethylbenzoic acid (Anca, Martinez-Carrera & Garcia-Blanco, 1967) and 48 ° in 2,4,6-trimethylbenzoic acid (Benghiat & Leiserowitz, 1972). The angle between the mean planes of the two transannularly located phenyl rings is 103 °.…”

“…It seemed reasonable, therefore, that incorporation of convergent functional groups into crown ether rings should have an influence on the stability of the ligand structure. In preceding papers we discussed the geometry of intramolecular interactions in two model compounds containing one 2-carboxy-l,3-xylyl unit as part of the polyether ring: 2,6-dimethylylbenzoic acid-18-crown-5 (Goldberg, 1976; referred to hereafter as BACR5) and 2,6-dimethylylbenzoic acid-2,6-dimethylylpyridine-18-crown-5 (Goldberg & Rezmovitz, 1978; referred to hereafter as BAPCR5). In both structures the carboxyl group is directed toward the center of the molecule, and hydrogen bonded to a transannularly located O (in BACRS) or N atom (in BAPCR5) nucleophile.…”

Contributions of Histochemistry to the Development of the Proteolytic Enzyme Detection System in Diagnostic Medicine

“…Although the place of enzyme-catalyzed reactions in clinical biochemistry has proven to be of diagnostic value since the late 1950s (16,17), it is only within the last 6 years that methods for determining the activity of proteases have been introduced into the clinical laboratory. Proteolytic enzymes are assuming increasing significance in biological regulation.…”