A gas-liquid chromatographic method for the determination of butriptyline in serum.

1. A gas-liquid chromatographic (GC) method for the analysis of butriptyline in serum has been development. Quantitation is based on the peak height ratio between butriptyline and promazine used as internal standard. A triple partition provides a "clean" extract. A detection limit of 10 ng/ml is achieved. 2. The usefulness of the method has been demonstrated in bioavailability studies in dogs.

A gas-liquid chromatographic determination of p-chlorophenoxyisobutyric acid and its comparison to an ultra violet method.

1. A gas-liquid chromatographic procedure for the determination of p-chlorophenoxyisobutyric acid (CPIB) has been elaborated and compared to the UV spectrophotometric procedure of Barrett and Thorp. 2. Both methods are specific when used to determine CPIB levels in normal sera from laboratory animals or humans treated with clofibrate (Atromid-S). Serum from patients treated with other drugs or abnormal sera from patients affected with a variety of diseases will often contain high and fluctuating levels of non-specific UV absorbing substances and this usually precludes the use of the UV procedure. 3. The GLC method is also applicable to the analysis of CPIB in urine samples.

Microcalorimetric study of the interaction of human and bovine serum albumins with tryptophan and tryptophan analogs.

The thermodynamic parameters for the protein-ligand binding have been obtained by microcalorimetry on three albumin samples (fatty acid free human serum albumin (I), fraction V human serum albumin (II), and fraction V bovine serum albumin (III)) bound with l-tryptophan (A) and three-ring tryptophan analogs (B and B*). The percentage, mu, of binding molecules (equivalent to the number of sites) is found to be 1.0 for I and 0.65 for II (in good agreement with dialysis results on the same systems) and 1.0 for III. The large negative delta H(bind) (-27.2 to -33.2 kJ . mol-1) constitutes the main contribution to delta G(bind) (-23.0 to -31.2 kJ . mol-1). The better binding of I-III towards B and B* compared with A is due to delta S(bind) being less negative. This is interpreted as a lesser loss of entropy for the three-ring ligands than for the normal tryptophan when they are bound. Data obtained on the proteins (heat of dilution; Huggins' constant, k') correlate well with mu or Qmax. This indicates that these physicochemical data could be used to characterize and compare rapidly some albumins of different sources. The unexpected finding that the parameters of I and III are nearer to each other than they are from II is discussed.

An investigation of the destruction of the beta-lactam ring of penems by the albumin drug-binding site.

The plasma proteins have been reported to exert irreversible effects on some beta-lactams. The penems represent a class of antibiotics of great interest due to their wide spectrum of activity. However, many compounds of this class were found to be unstable in rat serum. A prototype compound, (+/-)-2-methylpenem-3-carboxylic acid (BCL-98), was selected for detailed investigations. The capacity of penems to inhibit the destruction of a chromogenic beta-lactam (BCL-604) by serum was the technique selected to study the interaction of BCL-98 with serum proteins at the specific destructive site. The serum of various species was investigated and the magnitude of BCL-604 destruction was in the following order: rat = human greater than dog greater than mice. The human plasma proteins were fractionated on a Sephadex column and the fractions tested individually. The albumin fraction was found to be entirely responsible for the destruction, the globulin fractions being completely inactive. The reaction of Ellman's reagent with serum as not diminished in the presence of the BCL-98, thus demonstrating that the sulfhydryl group of albumin is not involved in this binding. Displacement of a fluorescent probe (5-dimethylaminonaphthalene-1-sulfonamide) by BCL-98 showed that the binding site for the latter is the same as the one occupied by L-tryptophan and thus involves the epsilon-lysine amino group of the albumin binding site. The exact nature of this binding is not yet established, but it can be inferred that it may involve acylation of the epsilon-lysine group at the binding site. Some analogs of BCL-98 were also investigated. The basic functionality seems to protect the molecule from the destructive site of the albumin, probably because this substituent induces binding at another nondestructive site resulting in a prolonged half-life in the blood.