Proteins are still gaining importance in the pharmaceutical world, where they are used to improve our arsenal of therapeutic drugs and vaccines and as diagnostic tools. Proteins are different from "traditional" low-molecular-weight drugs. As a group, they exhibit a number of biopharmaceutical and formulation problems. These problems have drawn considerable interest from both industrial and aca demic environments, forcing pharmaceutical scientists to explore a domain previ ously examined only by peptide and protein chemists. Biopharmaceutical aspects of proteins, e.g., low oral bioavailability, have been extensively investigated. Although all possible conventional routes of ad ministration have been examined for proteins, no real, generally applicable alter native to parenteral administration in order to achieve systemic effects has yet been discovered. Several of these biopharmaceutical options have been discussed in Volume 4 of this series, Biological Barriers to Protein Delivery. Proteins are composed of many amino acids, several of which are notorious for their chemical instability. Rational design of formulations that optimize the native structure and/or bioactivity of a protein is therefore of great importance when long shelf life is required, as it is for pharmaceutical products. This issue has also been examined in two prior volumes of this series: Volume 2: Stability of Protein Pharmaceuticals (Part A) and Volume 5: Stability and Characterization of Protein and Peptide Drugs."

Proteins are still gaining importance in the pharmaceutical world, where they are used to improve our arsenal of therapeutic drugs and vaccines and as diagnostic tools. Proteins are different from "traditional" low-molecular-weight drugs. As a group, they exhibit a number of biopharmaceutical and formulation problems. These problems have drawn considerable interest from both industrial and aca demic environments, forcing pharmaceutical scientists to explore a domain previ ously examined only by peptide and protein chemists. Biopharmaceutical aspects of proteins, e.g., low oral bioavailability, have been extensively investigated. Although all possible conventional routes of ad ministration have been examined for proteins, no real, generally applicable alter native to parenteral administration in order to achieve systemic effects has yet been discovered. Several of these biopharmaceutical options have been discussed in Volume 4 of this series, Biological Barriers to Protein Delivery. Proteins are composed of many amino acids, several of which are notorious for their chemical instability. Rational design of formulations that optimize the native structure and/or bioactivity of a protein is therefore of great importance when long shelf life is required, as it is for pharmaceutical products. This issue has also been examined in two prior volumes of this series: Volume 2: Stability of Protein Pharmaceuticals (Part A) and Volume 5: Stability and Characterization of Protein and Peptide Drugs.

Zeolites, with their crystalline microporous structures, are cordial hosts to a wide variety of guests. However, it was the abrupt and unexpected departure of one of these guests (water) from a host (stilbite) on heating which led Cronstedt, in 1756, to coin the term "zeolite" (from the Greek meaning "boiling stone") to describe this material. Since that time, approximately 40 different naturally-occurring zeolites have been discovered on earth. Recent studies of meteorite compositions have shown that these guest-host materials (e. g. , sodalite) occur in other parts of the universe as well. However, it wasn't until the twentieth century that synthetic routes to zeolites and other non-aluminosilicate molecular sieves were discovered. In addition, with the development of X-ray diffraction and the various spectroscopies, better understanding of the nature of the cavities, cages, and channels of these materials has led to the industrial exploitation of their guest-host properties. The world of zeolites has now expanded into a greater than 2 billion pound per year business, with major applications in detergent formulations, catalysis, and as adsorbents and desiccants. Their economic impact is difficult to determine; however, the improvement in gasoline yields alone (from catalytic cracking) must account for hundreds ofbillions ofdollars in increased GDP. In this volume, we have brought together a sampling of recent developments in various areas of guest-host or inclusion chemistry in zeolites.