Discovering the tertiary structure of a protein, or the quaternary structure of its complexes, can provide important clues about how the protein performs its function. Common experimental methods of structure determination include X-ray crystallography and NMR spectroscopy, both of which can produce information at atomic resolution. However, NMR experiments are able to provide information from which a subset of distances between pairs of atoms can be estimated, and the final possible conformations for a protein are determined by solving a distance geometry problem. Dual polarisation interferometry is a quantitative analytical method for measuring the overall protein conformation and conformational changes due to interactions or other stimulus. Circular dichroism is another laboratory technique for determining internal beta sheet/ helical composition of proteins. Cryoelectron microscopy is used to produce lower-resolution structural information about very large protein complexes, including assembled viruses; a variant known as electron crystallography can also produce high-resolution information in some cases, especially for two-dimensional crystals of membrane proteins. Solved structures are usually deposited in the Protein Data Bank (PDB), a freely available resource from which structural data about thousands of proteins can be obtained in the form of Cartesian coordinates for each atom in the protein.
Morphine is primarily used to treat both acute and chronic severe pain. It is also used for pain due to myocardial infarction and for labor pains. There are however concerns that morphine may increase mortality in the setting of non ST elevation myocardial infarction. Morphine has also traditionally been used in the treatment of acute pulmonary edema. A 2006 review however found little evidence to support this practice.
Other studies, such as the Rat Park experiments, suggest that morphine is less physically addictive than others suggest, and most studies on morphine addiction merely show that «severely distressed animals, like severely distressed people, will relieve their distress pharmacologically if they can.» In these studies, rats with a morphine «addiction» overcome their addiction themselves when placed in decent living environments with enough space, good food, companionship, areas for exercise, and areas for privacy. More recent research has shown that an enriched environment may decrease morphine addiction in mice.
Morphine-derived agonist—antagonist drugs have also been developed. Elements of the morphine structure have been used to create completely synthetic drugs such as the morphinan family (levorphanol, dextromethorphan and others) and other groups that have many members with morphine-like qualities. The modification of morphine and the aforementioned synthetics has also given rise to non-narcotic drugs with other uses such as emetics, stimulants, antitussives, anticholinergics, muscle relaxants, local anaesthetics, general anaesthetics, and others.
A number of salts of morphine are used, with the most common in current clinical use being the hydrochloride, sulfate, tartrate, and citrate; less commonly methobromide, hydrobromide, hydroiodide, lactate, chloride, and bitartrate and the others listed below. Morphine diacetate, which is another name for heroin, is a Schedule I controlled substance, so it is not used clinically in the United States; it is a sanctioned medication in the United Kingdom and in Canada and some countries in Continental Europe, its use being particularly common (nearly to the degree of the hydrochloride salt) in the United Kingdom. Morphine meconate is a major form of the alkaloid in the poppy, as is morphine pectinate, nitrate, sulphate, and some others. Like codeine, dihydrocodeine and other, especially older, opiates, morphine has been used as the salicylate salt by some suppliers and can be easily compounded, imparting the therapeutic advantage of both the opioid and the NSAID; multiple barbiturate salts of morphine were also used in the past, as was/is morphine valerate, the salt of the acid being the active principle of valerian. Calcium morphenate is the intermediate in various latex and poppy-straw methods of morphine production, more rarely sodium morphenate takes its place. Morphine ascorbate and other salts such as the tannate, citrate, and acetate, phosphate, valerate and others may be present in poppy tea depending on the method of preparation. Morphine valerate produced industrially was one ingredient of a medication available for both oral and parenteral administration popular many years ago in Europe and elsewhere called Trivalin (not to be confused with the current, unrelated herbal preparation of the same name), which also included the valerates of caffeine and cocaine, with a version containing codeine valerate as a fourth ingredient being distributed under the name Tetravalin.
Derivatives of plants of the genus Digitalis have a long history of medical use. The British physician William Withering is credited with the first published description of the use of digitalis derivatives in his 1785 book «An Account of the Foxglove and some of its Medical Uses With Practical Remarks on Dropsy and Other Diseases».