Proteins extraction, small molecule drug

Preservatives are necessary when developing multidose parenteral formulations that involve more than one extraction from the same container. Their primary function is to inhibit microbial growth and ensure product sterility throughout the shelf life or duration of use of the drug product. Commonly used preservatives include benzyl alcohol, phenol, and m-cresol. Although preservatives have a long history of use with small-molecule parenterals, the development of protein formulations that include... 

In order to form a crystal, molecules must aggregate in an orderly manner. This implies that intermolecular interactions have occurred in specific ways. It therefore follows that the crystal structure per se contains information on preferred modes of binding between the molecules in the crystalline state. In this Chapter we show how information on the most likely stereochemistries of interactions between functional groups in different molecules can be extracted from the three-dimensional coordinates of atoms listed in reports of crystal structure determinations. Three-dimensional structural data on binding stereochemistry may also be obtained from X-ray diffraction studies of the binding of small molecules to crystalline proteins and other macromolecules. These two types of information can be used, for example, to predict how drugs will interact with their biological receptors. 

If the compound is present at a low concentration in the presence of many interfering compounds, cleanup and concentration steps become necessary [8]. Solvent extraction procedures are used often for sample preparation for drugs and many other small molecules in the chromatographic technique. Solid-phase methods are very popular because of the wide choice of the packing material. Sample extraction methods have two other main advantages in CE, namely sample concentration and elimination of both sample ions and proteins. Double-solvent extraction is very useful for elec-trokinetic injection, especially for basic compounds. It eliminates variability due to matrix effects in electro-kinetic injection. 

Sample preparation efficiency is referred to recovery. The absolute recovery directly impacts assay sensitivity (i.e., LLOQ) of a method. Recovery can be measured precisely for small molecules by spiking a known amount of the analyte into blank matrix extracts. Recovery can be calculated by comparison of the response obtained from the postspiking samples with the response from extracted samples at the same concentration level(s). Becher and co-workers (2006) evaluated the overall extraction recovery for EPI-hNE4 in both human and monkey plasma of an LC—MS/MS assay using protein precipitation as the sample preparation. The recovery for EPI-hNE4 was determined to be between 44.1 and 48.8%, while the recovery for the ISTD was 43.4%. Ji and coworkers (2003) used SPE to extract rK5, a small protein drug, from plasma... 

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