The G-protein's α subunit, together with the bound GTP, can then dissociate from the β and γ subunits to further affect intracellular signaling proteins or target functional proteins directly depending on the α subunit type ( G < sub > αs </ sub >, G < sub > αi / o </ sub >, G < sub > αq / 11 </ sub >, G < sub > α12 / 13 </ sub >).

These proteins are homologous to the alpha ( α ) subunit found in heterotrimers, and are in fact monomeric.

When a ligand activates the G protein-coupled receptor, it induces a conformational change in the receptor that allows the receptor to function as a guanine nucleotide exchange factor ( GEF ) that exchanges GDP for GTP on the G < sub > α </ sub > subunit.

In the traditional view of heterotrimeric protein activation, this exchange triggers the dissociation of the G < sub > α </ sub > subunit, bound to GTP, from the G < sub > βγ </ sub > dimer and the receptor.

The G < sub > α </ sub > subunit will eventually hydrolyze the attached GTP to GDP by its inherent enzymatic activity, allowing it to re-associate with G < sub > βγ </ sub > and starting a new cycle.

This is an alternate form of regulation for the G < sub > α </ sub > subunit.

These proteins are homologous to the alpha ( α ) subunit found in heterotrimers, but exist as monomers.

In adult humans, the most common hemoglobin type is a tetramer ( which contains 4 subunit proteins ) called hemoglobin A, consisting of two α and two β subunits non-covalently bound, each made of 141 and 146 amino acid residues, respectively.

For most voltage-gated ion channels, the pore-forming subunit ( s ) are called the α subunit, while the auxiliary subunits are denoted β, γ, and so on.

Tubulin polymerizes end to end with the α subunit of one tubulin dimer contacting the β subunit of the next.

Therefore, in a protofilament, one end will have the α subunit exposed while the other end will have the β subunit exposed.

In archaea such as Thermoplasma acidophilum, all the α and all the β subunits are identical, whereas eukaryotic proteasomes such as those in yeast contain seven distinct types of each subunit.

But certain benzodiazepines ( hypnotic benzodiazepines ) have significantly higher activity at the α < sub > 1 </ sub > subunit of the GABA < sub > A </ sub > receptor compared to other benzodiazepines ( for example, triazolam and temazepam have significantly higher activity at the α < sub > 1 </ sub > subunit compared to alprazolam and diazepam, making them superior sedative-hypnotics – alprazolam and diazepam in turn have higher activity at the α < sub > 2 </ sub > subunit compared to triazolam and temazepam, making them superior anxiolytic agents ).

Alpha ( uppercase Α, lowercase α ; Álpha ) is the first letter of the Greek alphabet.

* α Antliae is the constellation's brightest star at magnitude 4. 25.

* α Apodis is an orange giant 411 light years away, with a magnitude of 3. 8.

Arcturus (; α Boo, α Boötis, Alpha Boötis ) is the brightest star in the constellation Boötes and in fact the northern celestial hemisphere.

This makes Arcturus the third brightest individual star, just ahead of Alpha Centauri A ( α Cen A ), whose visual magnitude is − 0. 01.

Arcturus is notable for its high proper motion, larger than any first magnitude star in the stellar neighborhood other than α Centauri.

Antares ( α Scorpii, α Sco, Alpha Scorpii ) is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime sky.

Altair ( Alpha Aquilae, Alpha Aql, α Aquilae, α Aql, Atair ) is the brightest star in the constellation Aquila and the twelfth brightest star in the night sky.

In Chinese, the asterism consisting of α, β, and γ Aquilae is known as (, ).

Alioth has a relatively weak magnetic field, 15 times weaker than α CVn, but it is still 100 times stronger than that of the Earth.

It contains both α and β ' phase ; the β '- phase is body-centered cubic and is harder and stronger than α. Alpha-beta brasses are usually worked hot.

) For example, Aldebaran is designated α Tauri ( pronounced Alpha Tauri ), which means " Alpha of the Bull ".

Since in a majority of constellations the brightest star is designated Alpha ( α ), many people wrongly assume that Bayer meant to put the stars exclusively in order of their brightness, but in his day there was no way to measure stellar brightness precisely.

Although α and − α produce the same differential equation, it is conventional to define different Bessel functions for these two orders ( e. g., so that the Bessel functions are mostly smooth functions of α ).

On the other hand, for integer order α, the following relationship is valid ( note that the Gamma function becomes infinite for negative integer arguments ):

For non-integer α, Y < sub > α </ sub >( x ) is related to J < sub > α </ sub >( x ) by:

α < sup > 1 </ sup > is itself a spectroscopic binary star, with its components thought to be around 14 and 10 times the mass of the Sun and orbiting in only 76 days at a separation of about 1 AU.

Though T < sub > βγ </ sub > has been mentioned to be crucial for T < sub > α </ sub > binding to rhodopsin, there is also evidence that T < sub > βγ </ sub > may have a crucial, possibly direct role in nucleotide exchange than previously thought.

Evidence has shown that cigarette smoke can lead to oxidation of methionine 358 of α < sub > 1 </ sub >- antitrypsin ( 382 in the pre-processed form containing the 24 amino acid signal peptide ), a residue essential for binding elastase ; this is thought to be one of the primary mechanisms by which cigarette smoking ( or second-hand smoke ) can lead to emphysema.

From studying its light curve during occultation, it is thought that α Cancri A may itself be a close binary, consisting of two stars with similar brightness and a separation of 0. 1 arcseconds.

Structurally they can be classified according to the functional groups ' locations as alpha-( α -), beta-( β -), gamma-( γ -) or delta-( δ -) amino acids ; other categories relate to polarity, acid / base / neutral, and side chain group type ( including: aliphatic, acyclic, hydroxyl or sulphur-containing, aromatic ).

It exists in four major polymorphs: α, β, γ and T. Whereas α, β and T phases are based on B < sub > 12 </ sub > icosahedra, the γ-phase can be described as a rocksalt-type arrangement of the icosahedra and B < sub > 2 </ sub > atomic pairs.

It can be considered as a ' natural ' partner of J < sub > α </ sub >( x ).

If α is an integer, the limit has to be calculated.

This orthogonality relation can then be used to extract the coefficients in the Fourier – Bessel series, where a function is expanded in the basis of the functions J < sub > α </ sub >( x u < sub > α, m </ sub >) for fixed α and varying m.

The name context-sensitive is explained by the α and β that form the context of A and determine whether A can be replaced with γ or not.

However, most of the brightest stars of Centaurus, including α Cen, θ Cen, ε Cen and η Cen, can be seen in the Chinese sky.

and, again, by shifting the position of the y-axis, α can be taken to be 0.

As before, the x and y-axes can be shifted so α and β can be taken to be 0.

Again, the x and y-axes can be shifted so α and β can be taken to be 0.

which can be recognized as a circular path around the origin with radius α.

Crick was witness to the kinds of errors that his co-workers made in their failed attempts to make a correct molecular model of the α helix ; these turned out to be important lessons that could be applied, in the future, to the helical structure of DNA.

The heterotrimeric G proteins can be classified by sequence homology of the α unit into four families:

By combination of different α, β and γ subunits, a great variety (> 1000 ) G proteins can be produced.

* Hemoglobin H ( β < sub > 4 </ sub >)-A variant form of hemoglobin, formed by a tetramer of β chains, which may be present in variants of α thalassemia.

* Hemoglobin Barts ( γ < sub > 4 </ sub >)-A variant form of hemoglobin, formed by a tetramer of γ chains, which may be present in variants of α thalassemia.