text stringlengths 0 3.86k |
|---|
Several factors led to the Frank Slide . A study conducted by the GSC immediately following the slide concluded that the primary cause was the mountain 's unstable anticline formation ; a layer of limestone rested on top of softer materials that , after years of erosion , resulted in a top @-@ heavy , steep cliff . Cr... |
An unusually warm winter , with warm days and cold nights , was also a factor . Water in the mountain 's fissures froze and thawed repeatedly , further weakening the mountain 's supports . Heavy snowfall in the region in March was followed by a warm April , causing the mountain snows to melt into the fissures . GSC ge... |
Though the GSC concluded that mining activities contributed to the slide , the facility 's owners disagreed . Their engineers claimed that the mine bore no responsibility . Later studies suggested that the mountain had been at a point of " equilibrium " ; even a small deformation such as that caused by the mine 's exi... |
The slide created two new peaks on the mountain ; the south peak stands 2 @,@ 200 metres ( 7 @,@ 200 ft ) high and the north peak 2 @,@ 100 metres ( 6 @,@ 900 ft ) . Geologists believe that another slide is inevitable , though not imminent . The south peak is considered the most likely to fall ; it would likely create... |
Geologists have debated about what caused the slide debris to travel the distance it did . The " air cushion " theory , an early hypothesis , postulated that a layer of air was trapped between the mass of rock and the mountain , which caused the rock to move a greater distance than would otherwise be expected . " Acou... |
= = Legends = =
|
Numerous legends and misconceptions were spawned in the aftermath of the slide . The entire town of Frank was claimed to have been buried , though much of the town itself was unscathed . The belief that a branch of the Union Bank of Canada had been buried with as much as $ 500 @,@ 000 persisted for many years . The ba... |
Several people , telling amazing stories to those who would listen , passed themselves off as the " sole survivor " in the years following the slide . The most common such tale is that of an infant girl said to have been the only survivor of the slide . Her real name unknown , the girl was called " Frankie Slide " . S... |
= = Legacy = =
|
Curious sightseers flocked to the site of the slide within the day of the disaster . It has remained a popular tourist destination , in part due to its proximity to the Crowsnest Highway . The province built a roadside turnout in 1941 to accommodate the traffic . Town boosters unsuccessfully sought to have the site de... |
Though Frank recovered from the slide and achieved a peak population of 1 @,@ 000 shortly thereafter , the closure of the mine resulted in a longstanding decline in population . Frank ceased to be an independent community in 1979 when it was amalgamated into the Municipality of Crowsnest Pass along with the neighbouri... |
= Protein =
|
Proteins ( / ˈproʊˌtiːnz / or / ˈproʊti.ᵻnz / ) are large biomolecules , or macromolecules , consisting of one or more long chains of amino acid residues . Proteins perform a vast array of functions within organisms , including catalysing metabolic reactions , DNA replication , responding to stimuli , and transporting... |
A linear chain of amino acid residues is called a polypeptide . A protein contains at least one long polypeptide . Short polypeptides , containing less than 20 @-@ 30 residues , are rarely considered to be proteins and are commonly called peptides , or sometimes oligopeptides . The individual amino acid residues are b... |
Once formed , proteins only exist for a certain period of time and are then degraded and recycled by the cell 's machinery through the process of protein turnover . A protein 's lifespan is measured in terms of its half @-@ life and covers a wide range . They can exist for minutes or years with an average lifespan of ... |
Like other biological macromolecules such as polysaccharides and nucleic acids , proteins are essential parts of organisms and participate in virtually every process within cells . Many proteins are enzymes that catalyse biochemical reactions and are vital to metabolism . Proteins also have structural or mechanical fu... |
Proteins may be purified from other cellular components using a variety of techniques such as ultracentrifugation , precipitation , electrophoresis , and chromatography ; the advent of genetic engineering has made possible a number of methods to facilitate purification . Methods commonly used to study protein structur... |
= = Biochemistry = =
|
Most proteins consist of linear polymers built from series of up to 20 different L @-@ α @-@ amino acids . All proteinogenic amino acids possess common structural features , including an α @-@ carbon to which an amino group , a carboxyl group , and a variable side chain are bonded . Only proline differs from this basi... |
The peptide bond has two resonance forms that contribute some double @-@ bond character and inhibit rotation around its axis , so that the alpha carbons are roughly coplanar . The other two dihedral angles in the peptide bond determine the local shape assumed by the protein backbone . The end of the protein with a fre... |
= = = Abundance in cells = = =
|
It has been estimated that average @-@ sized bacteria contain about 2 million proteins per cell ( e.g. E. coli and Staphylococcus aureus ) . Smaller bacteria , such as Mycoplasma or spirochetes contain fewer molecules , namely on the order of 50 @,@ 000 to 1 million . By contrast , eukaryotic cells are larger and thus... |
Importantly , the concentration of individual proteins ranges from a few molecules per cell to hundreds of thousands . In fact , about a third of all proteins is not produced in most cells or only induced under certain circumstances . For instance , of the 20 @,@ 000 or so proteins encoded by the human genome only 6 @... |
= = Synthesis = =
|
= = = Biosynthesis = = =
|
Proteins are assembled from amino acids using information encoded in genes . Each protein has its own unique amino acid sequence that is specified by the nucleotide sequence of the gene encoding this protein . The genetic code is a set of three @-@ nucleotide sets called codons and each three @-@ nucleotide combinatio... |
The process of synthesizing a protein from an mRNA template is known as translation . The mRNA is loaded onto the ribosome and is read three nucleotides at a time by matching each codon to its base pairing anticodon located on a transfer RNA molecule , which carries the amino acid corresponding to the codon it recogni... |
The size of a synthesized protein can be measured by the number of amino acids it contains and by its total molecular mass , which is normally reported in units of daltons ( synonymous with atomic mass units ) , or the derivative unit kilodalton ( kDa ) . Yeast proteins are on average 466 amino acids long and 53 kDa i... |
= = = Chemical synthesis = = =
|
Short proteins can also be synthesized chemically by a family of methods known as peptide synthesis , which rely on organic synthesis techniques such as chemical ligation to produce peptides in high yield . Chemical synthesis allows for the introduction of non @-@ natural amino acids into polypeptide chains , such as ... |
= = Structure = =
|
Most proteins fold into unique 3 @-@ dimensional structures . The shape into which a protein naturally folds is known as its native conformation . Although many proteins can fold unassisted , simply through the chemical properties of their amino acids , others require the aid of molecular chaperones to fold into their... |
Primary structure : the amino acid sequence . A protein is a polyamide .
|
Secondary structure : regularly repeating local structures stabilized by hydrogen bonds . The most common examples are the α @-@ helix , β @-@ sheet and turns . Because secondary structures are local , many regions of different secondary structure can be present in the same protein molecule .
|
Tertiary structure : the overall shape of a single protein molecule ; the spatial relationship of the secondary structures to one another . Tertiary structure is generally stabilized by nonlocal interactions , most commonly the formation of a hydrophobic core , but also through salt bridges , hydrogen bonds , disulfid... |
Quaternary structure : the structure formed by several protein molecules ( polypeptide chains ) , usually called protein subunits in this context , which function as a single protein complex .
|
Proteins are not entirely rigid molecules . In addition to these levels of structure , proteins may shift between several related structures while they perform their functions . In the context of these functional rearrangements , these tertiary or quaternary structures are usually referred to as " conformations " , an... |
Proteins can be informally divided into three main classes , which correlate with typical tertiary structures : globular proteins , fibrous proteins , and membrane proteins . Almost all globular proteins are soluble and many are enzymes . Fibrous proteins are often structural , such as collagen , the major component o... |
A special case of intramolecular hydrogen bonds within proteins , poorly shielded from water attack and hence promoting their own dehydration , are called dehydrons .
|
= = = Structure determination = = =
|
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 informatio... |
Many more gene sequences are known than protein structures . Further , the set of solved structures is biased toward proteins that can be easily subjected to the conditions required in X @-@ ray crystallography , one of the major structure determination methods . In particular , globular proteins are comparatively eas... |
= = Cellular functions = =
|
Proteins are the chief actors within the cell , said to be carrying out the duties specified by the information encoded in genes . With the exception of certain types of RNA , most other biological molecules are relatively inert elements upon which proteins act . Proteins make up half the dry weight of an Escherichia ... |
The chief characteristic of proteins that also allows their diverse set of functions is their ability to bind other molecules specifically and tightly . The region of the protein responsible for binding another molecule is known as the binding site and is often a depression or " pocket " on the molecular surface . Thi... |
Proteins can bind to other proteins as well as to small @-@ molecule substrates . When proteins bind specifically to other copies of the same molecule , they can oligomerize to form fibrils ; this process occurs often in structural proteins that consist of globular monomers that self @-@ associate to form rigid fibers... |
= = = Enzymes = = =
|
The best @-@ known role of proteins in the cell is as enzymes , which catalyse chemical reactions . Enzymes are usually highly specific and accelerate only one or a few chemical reactions . Enzymes carry out most of the reactions involved in metabolism , as well as manipulating DNA in processes such as DNA replication... |
The molecules bound and acted upon by enzymes are called substrates . Although enzymes can consist of hundreds of amino acids , it is usually only a small fraction of the residues that come in contact with the substrate , and an even smaller fraction — three to four residues on average — that are directly involved in ... |
Dirigent proteins are members of a class of proteins that dictate the stereochemistry of a compound synthesized by other enzymes .
|
= = = Cell signaling and ligand binding = = =
|
Many proteins are involved in the process of cell signaling and signal transduction . Some proteins , such as insulin , are extracellular proteins that transmit a signal from the cell in which they were synthesized to other cells in distant tissues . Others are membrane proteins that act as receptors whose main functi... |
Antibodies are protein components of an adaptive immune system whose main function is to bind antigens , or foreign substances in the body , and target them for destruction . Antibodies can be secreted into the extracellular environment or anchored in the membranes of specialized B cells known as plasma cells . Wherea... |
Many ligand transport proteins bind particular small biomolecules and transport them to other locations in the body of a multicellular organism . These proteins must have a high binding affinity when their ligand is present in high concentrations , but must also release the ligand when it is present at low concentrati... |
Transmembrane proteins can also serve as ligand transport proteins that alter the permeability of the cell membrane to small molecules and ions . The membrane alone has a hydrophobic core through which polar or charged molecules cannot diffuse . Membrane proteins contain internal channels that allow such molecules to ... |
= = = Structural proteins = = =
|
Structural proteins confer stiffness and rigidity to otherwise @-@ fluid biological components . Most structural proteins are fibrous proteins ; for example , collagen and elastin are critical components of connective tissue such as cartilage , and keratin is found in hard or filamentous structures such as hair , nail... |
Other proteins that serve structural functions are motor proteins such as myosin , kinesin , and dynein , which are capable of generating mechanical forces . These proteins are crucial for cellular motility of single celled organisms and the sperm of many multicellular organisms which reproduce sexually . They also ge... |
= = Methods of study = =
|
The activities and structures of proteins may be examined in vitro , in vivo , and in silico . In vitro studies of purified proteins in controlled environments are useful for learning how a protein carries out its function : for example , enzyme kinetics studies explore the chemical mechanism of an enzyme 's catalytic... |
= = = Protein purification = = =
|
To perform in vitro analysis , a protein must be purified away from other cellular components . This process usually begins with cell lysis , in which a cell 's membrane is disrupted and its internal contents released into a solution known as a crude lysate . The resulting mixture can be purified using ultracentrifuga... |
For natural proteins , a series of purification steps may be necessary to obtain protein sufficiently pure for laboratory applications . To simplify this process , genetic engineering is often used to add chemical features to proteins that make them easier to purify without affecting their structure or activity . Here... |
= = = Cellular localization = = =
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.