Natural fiber exoskeletons of insects and arthropods. In shells and exoskeletons, the chitin fibers contribute to their hierarchical structure. In nature, pure chitin (100% acetylation) does not exist. It instead exists as a copolymer with chitin's deacetylated derivative, chitosan. When the acetylized composition of the copolymer is over 50% acetylated it is chitin. This copolymer of chitin and chitosan is a random or block copolymer. Chitosan is a deacetylated derivative of chitin. When the acetylized composition of the copolymer is below 50% it is chitosan. Chitosan is a semicrystalline “polymer of β-(1-4)-2-amino-2-deoxy-D-glucose”. One difference between chitin and chitosan is that chitosan is
Doctor of Pharmacy holders to pursue an academic career by enrolling masters and doctorates programs (MSc and PhD) in several scientific fields (pharmaceutical technology, pharmacokinetics and biopharmaceutics, biomedical sciences, cosmetics & pharmaceutical industry, pharmaceutical and organic chemistry, physical chemistry, food sciences, pharmacology, toxicology, public health, etc.). Masters usually lasts 1–2 years and PhD's no less than 4 years. In summary, in Spain an entry-level pharmacy degree lasts 5 years and a "Hospital Pharmacy Specialist" needs 9.5 years of education and/or training. Hospital Pharmacy Residents are paid during their residency period. There are other residencies available to pharmacists such as Medical Biology, Clinical Biochemistry,