The diversity of the conformations may have led to different forms of the prion diseases.An unusual secondary structure named alpha sheet has been proposed as the toxic constituent of amyloid precursor proteins. This idea is not widely accepted at present, but a fair amount of evidence has accumulated, especially recently, in its favor. Definition
The name amyloid comes from the early mistaken identification by Rudolf Virchow of the substance as starch (amylumcode: lat promoted to code: la  in Latin, from Ancient Greek: ἄμυλον, romanized: amylon), based on crude iodine-staining techniques. For a period, the scientific community debated whether or not amyloid deposits are fatty deposits or carbohydrate deposits until it was finally found (in 1859) that they are, in fact, deposits of albumoid proteinaceous material. The classical, histopathological definition of amyloid is an extracellular, proteinaceous fibrillar deposit exhibiting β-sheet secondary structure and identified by apple-green birefringence when stained with congo red under polarized light. These deposits often recruit various sugars and other components such as serum amyloid P component, resulting in complex, and sometimes inhomogeneous structures. Recently this definition has come into question as some classic, amyloid species have been observed in distinctly intracellular locations. A more recent, biophysical definition is broader, including any polypeptide that polymerizes to form a cross-β structure, in vivo or in vitro, inside or outside cells. Microbiologists, biochemists, biophysicists, chemists and physicists have largely adopted this definition, leading to some conflict in the biological community over an issue of language.
Institute of Technology, a university in Bangalore, India
Providence Elementary School, an elementary school in Chesterfield County, Virginia

Computing
Pro Evolution Soccer, a multi-platform video game series developed by Konami
Packetized elementary stream, part of the MPEG communication protocol
Peripheral Event System, an implementation of autonomous peripheral operations in microcontrollers
PSTN Emulation System for IP Multimedia Subsystem (IMS)

Organizations
Postal Express Service, United States military mail during World War I
Power Engineering Society, now the Power & Energy Society of the Institute of Electrical and Electronics Engineers
Premier Election Solutions, formerly Diebold Election Systems
Party of European Socialists, a centre-left pan-European political party
Social Encounter Party, a Mexican former political party
Solidarity Encounter Party, a Mexican former political party

Science
Pallasite Eagle Station, a pallasite meteorite grouplet
Photoemission spectroscopy, a measurement of a substances binding energy using the photoelectric effect
Poly(ethylene succinate), a type of polyester
Polyester, an artificially produced organic chemical that is spun and woven to make fabric
Polyethersulfone, a thermoplastic polymer
Potential energy surface, in physics and chemistry
Programmed electrical stimulation, a type of electrophysiologic study
Pseudoexfoliation syndrome, an eye problem

Other
PES (director) (born 1973), film director and animator born Adam Pesapane
Passenger Environment Survey, quality-control system for transit systems
Payment for ecosystem services, incentives offered to farmers or landowners
Pensarn railway station, Gwynedd, Wales, by National Rail station code
Price elasticity of supply, a measure used in economics
PULHHEEMS, a system of grading physical and mental fitness used by Britains armed forces

See also
Pez (disambiguation)