Amyloids are insoluble fibrous protein aggregates sharing specific structural traits. Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl Abnormal accumulation of amyloid in organs may lead to amyloidosis, and may play a role in various other neurodegenerative diseases. In Medicine, amyloidosis refers to a variety of conditions in which Amyloid Proteins are abnormally deposited in organs and/or tissues

Definition controversy

The name amyloid comes from the early mistaken identification of the substance as starch (amylum in Latin), based on crude iodine-staining techniques. Starch, CAS # 9005-25-8 Chemical formula (C6H10O5n is a Polysaccharide Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. For a period, the scientific community debated whether or not amyloid deposits were fatty deposits or carbohydrate deposits until it was finally resolved that it was neither, but rather a deposition of proteinaceous mass. Lipids are broadly defined as any fat- Soluble ( lipophilic) naturally-occurring Molecule, such as fats oils waxes cholesterol sterols fat-soluble Carbohydrates (from ' Hydrates of Carbon ' or saccharides ( Greek σάκχαρον meaning " Sugar " are the most ^[1]

• The classical, histopathological definition of amyloid is an extracellular, proteinaceous deposit exhibiting beta sheet structure. Histopathology (from the Greek histos (tissue and pathos (suffering refers to the microscopic examination of tissue in order to study the manifestations The β sheet (also β-pleated sheet) is the second form of regular Secondary structure in Proteins consisting of beta strands connected laterally This is due to mis-folding of unstable proteins. Common to most cross-beta type structures they are generally identified by apple-green birefringence when stained with congo red and seen under polarized light. Birefringence, or double refraction, is the decomposition of a ray of Light into two rays (the ordinary ray and the extraordinary ray Congo red is the sodium salt of benzidinediazo-bis-1-naphtylamine-4-sulfonic acid (formula C32H22N6Na2O6S2 molecular Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations These deposits often recruit various sugars and other components such as Serum Amyloid P component, resulting in complex, and sometimes inhomogeneous structures. Amyloid P component serum (SAP is the identical serum form of amyloid P component (AP a 25kDa pentameric Protein first identified as the pentagonal constituent of in vivo ^[2] 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 which adopts a cross-beta polymerization, in vivo, or in vitro. Some of these, although demonstrably cross-beta sheet, fail other characteristic tests of amyloid, such as the Congo red birefringence test. Microbiologists and biophysicists have largely adopted this definition, leading to some conflict in the biological community over an issue of language. In Linguistics, prescription can refer both to the codification and the enforcement of rules governing how a language is to be used

The remainder of this article will be inclusive with due deference to the controversy by indicating where amyloid species are observed only in the biophysical context.

Diseases featuring amyloids

• Medullary carcinoma of the thyroid
• Amyloidosis
• Alzheimer's disease
• Transmissible spongiform encephalopathy
• Type 2 diabetes mellitus
• Yeast Prions [Sup35],^[3] Rnq1
• Sporadic Inclusion Body Myositis (S-IBM)
• pheochromocytoma
• Osteomyelitis

Non-disease amyloids

(mostly using the biophysical definition)

• Native amyloids in organisms
  • Curli E. coli Protein (curlin)
  • Podospora Anserina Prion Het-s
  • Malarial coat protein
  • Spider silk (some but not all spiders)
  • Mammalian melanosomes (pMel)
  • Tissue-type plasminogen activator (tPA), a hemodynamic factor
• Proteins and peptides known to make amyloid without any known disease
  • Calcitonin
• Proteins and peptides engineered to make amyloid

Amyloid biophysics

Amyloid is characterized by a cross-beta sheet quaternary structure; that is, the beta-strands of the stacked beta-sheets come from different protein monomers and align perpendicular to the axis of the fibril. Medullary thyroid cancer is a form of thyroid carcinoma which originates from the Parafollicular cells (C cells which produce the hormone Calcitonin. In Medicine, amyloidosis refers to a variety of conditions in which Amyloid Proteins are abnormally deposited in organs and/or tissues Alzheimer's disease ( AD) also called Alzheimer disease or simply Alzheimer's, is the most common form of Dementia. Transmissible spongiform encephalopathies' ( TSEs, also known as prion diseases) are a group of progressive conditions that affect the Brain and Diabetes mellitus type 2 or Type 2 Diabetes (formerly called non - Insulin -dependent Diabetes mellitus (NIDDM or adult-onset diabetes is a metabolic Sporadic inclusion body myositis ( sIBM) is an inflammatory Muscle Disease, characterized by slowly progressive weakness and wasting of the A phaeochromocytoma ( pheochromocytoma in the US is a Neuroendocrine tumor of the medulla of the Adrenal glands (originating in the Chromaffin Malaria is a vector -borne Infectious disease caused by Protozoan Parasites It is widespread in tropical and subtropical regions including Spider silk, also known as Gossamer, is a Protein Fiber spun by Spiders Spiders use their silk to make webs or other structures which function In a biological cell, a melanosome is an Organelle containing Melanin, the most common light-absorbing pigment found in the animal kingdom Calcitonin is a 32-amino acid linear polypeptide Hormone that is produced in Humans primarily by the parafollicular (also known as C-cells of the The β sheet (also β-pleated sheet) is the second form of regular Secondary structure in Proteins consisting of beta strands connected laterally In Biochemistry, quaternary structure is the arrangement of multiple folded Protein molecules in a multi-subunit complex While amyloid is usually identified using fluorescent dyes, stain polarimetry, circular dichroism, or FTIR (all indirect measurements), the "gold-standard" test to see if a structure contains cross-beta fibres is by placing a sample in an X-ray diffraction beam. X-radiation (composed of X-rays) is a form of Electromagnetic radiation. There are two characteristic scattering diffraction signals produced at 4. 7 and 10 Ångstroms (0. An ångström or angstrom (symbol Å) (ˈɔːŋstrəm Swedish: ˈɔ̀ŋstrœm is an internationally recognized non- SI unit of length equal 47 nm and 1. 0 nm), corresponding to the interstrand and stacking distances in beta sheets. It should be noted that the "stacks" of beta sheet are short and traverse the breadth of the amyloid fibril; the length of the amyloid fibril is built by aligned strands.

Amyloid polymerization (aggregation or non-covalent polymerization) is generally sequence-sensitive, that is, causing mutations in the sequence can prevent self-assembly, especially if the mutation is a beta-sheet breaker, such as proline. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds For example, humans produce an amyloidogenic peptide associated with type II diabetes, but, in Rodentia, a proline is substituted in a critical location and amyloidogenesis does not occur. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Rodentia is an order of Mammals also known as rodents, characterised by two continuously-growing incisors in the upper and lower jaws which must

There are two broad classes of amyloid-forming polypeptide sequences. Glutamine-rich polypeptides are important in the amyloidogenesis of Yeast and mammalian prions, as well as Huntington's disease. A prion (ˈpriːɒn is thought to be an infectious agent that according to current scientific consensus is comprised entirely of a propagated, mis-folded When peptides are in a beta-sheet conformation, particularly when the residues are parallel and in-register (causing alignment), glutamines can brace the structure by forming intrastrand hydrogen bonding between its amide carbonyls and nitrogens. In general, for this class of diseases, toxicity correlates with glutamine content. This has been observed in studies of onset age for Huntington's disease (the longer the polyglutamine sequence, the sooner the symptoms appear), and has been confirmed in a C. elegans model system with engineered polyglutamine peptides. Huntington's disease, also called Huntington's chorea, chorea major, or HD, is a genetic neurological disorder characterized after Caenorhabditis elegans (ˌsiːnoʊræbˈdaɪtɪs ˈɛlɪgænz is a free-living Nematode (roundworm about 1  mm in length which

Other polypeptides and proteins such as amylin and the Alzheimer's beta protein do not have a simple consensus sequence and are thought to operate by hydrophobic association. Amylin or Islet Amyloid Polypeptide (IAPP is a 37-residue Peptide hormone secreted by pancreatic β-cells at the same time as Insulin Among the hydrophobic residues, aromatic amino-acids are found to have the highest amyloidogenic propensity.

For these peptides, cross-polymerization (fibrils of one polypeptide sequence causing other fibrils of another sequence to form) is a phenomenon observed in vitro. This phenomenon is important since it would explain interspecies prion propagation and Amyloid biophysics differential rates of propagation, as well as a statistical link between Alzheimer's and diabetes. A prion (ˈpriːɒn is thought to be an infectious agent that according to current scientific consensus is comprised entirely of a propagated, mis-folded In general, cross-polymerization is more efficient the more similar the peptide sequence, though entirely dissimilar sequences can cross-polymerize and highly similar sequences can even be "blockers" which prevent polymerization. Polypeptides will not cross-polymerize their mirror-image counterparts, indicating that the phenomenon involves specific binding and recognition events.

Xu, using atomic force microscopy, has shown in both lysozyme and human tau40 that formation of amyloid fibers is a two-step process in which proteins first aggregate into uniform colloidal spheres of ~20nm diameter. ^[4] The spheres then join to form characteristic linear chains, which evolve over time into mature amyloid fibers. He proposes that aggregation drives conformational change and that a conformational change is not essential to initiate the aggregation process.

Amyloid pathology

The reasons for amyloid association with disease is unclear. In many cases, the deposits physically disrupt tissue architecture, suggesting disruption of function by some bulk process. In other cases, cell death is believed to precede amyloid deposition, suggesting small amyloid-like oligomers (possibly but not necessarily biophysically amyloid) cause cell death. There is significant speculation that amyloid fibrils can also puncture cells or cause problems such as ionic imbalance in cells. Further speculation has led to the hypothesis that while amyloid association may be the cause of health issues, the association itself is initiated by an underlying problem, such as one/some of the above mentioned side effects like calcium ion concentration imbalances.

Histological staining

Clinically, amyloid diseases are typically identified by a change in the fluorescence intensity of planar aromatic dyes such as thioflavin T or congo red. Fluorescence is a Luminescence that is mostly found as an A dye can generally be described as a Colored substance that has an affinity to the substrate to which it is being applied Thioflavin can refer to either of two dyes used for Histology staining Congo red is the sodium salt of benzidinediazo-bis-1-naphtylamine-4-sulfonic acid (formula C32H22N6Na2O6S2 molecular Congo red positivity remains the gold standard for diagnosis of amyloidosis. This is generally attributed to the environmental change, as these dyes intercalate between beta-strands. Congophilic amyloid plaques generally cause apple-green birefringence, when viewed through crossed polarimetric filters. To avoid nonspecific staining, histology stains, such as hematoxylin and eosin stain, are used to quench the dyes' activity in other places where the dye might bind, such as the nucleus. Histology (from the Greek = 'tissue' is the study of the microscopic anatomy of cells and tissues of Plants and H&E stain, HE stain or hematoxylin and eosin stain, is a popular Staining method in Histology. Modern antibody technology and immunohistochemistry has made specific staining easier, but often this can cause trouble because epitopes can be concealed in the amyloid fold; an amyloid protein structure is generally a different conformation from that which the antibody recognizes. Immunohistochemistry or IHC refers to the process of localizing proteins in cells of a tissue section exploiting the principle of antibodies binding specifically

References

External links

• Amyloid Peptides at Bachem. com
• Amyloid Precursor Protein, CTF fragments at rpeptide. com
• Amyloid Treatment and Research Program at Boston University
• Amyloid: Journal of Protein Folding Disorders web page at tandf. For similarly-named academic institutions see Education in Boston MA. co. uk
• Amyloidosis web page at Cornell University
• Information, support and advice to anyone with Amyloidosis, particularly in Australia (www. amyloidosisaustralia. org)
• Amyloidosis Support Network at amyloidosis. org
• UK National Amyloidosis Centre - one of the largest amyloid diagnosis and research centres at ucl. ac. uk
• Engineering Amyloid for material at University of California, Berkeley
• Amyloidosis Foundation amyloidosisresearchfoundation. The University of California Berkeley (also referred to as Cal, Berkeley and UC Berkeley) is a major research university located in Berkeley org
• National Kidney and Urologic Diseases Information Clearinghouse at National Institute of Health
• Eubanks L, Rogers C, Beuscher A, Koob G, Olson A, Dickerson T, Janda K (2006). "NIH" redirects here For other meanings of NIH see NIH (disambiguation. "A molecular link between the active component of marijuana and Alzheimer's disease pathology". Mol. Pharm. 3 (6): 773-7. doi:10.1021/mp060066m. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17140265.