Cycloleucine is a non-proteinogenic amino acid.

Since the circulating thyroid hormones are the amino acids thyroxine and tri-iodothyronine ( cf. Section C ), it is clear that some mechanism must exist in the thyroid gland for their release from proteins before secretion.

It lacks the NH < sub > 2 </ sub > group because of the cyclization of the side-chain and is known as an imino acid ; it falls under the category of special structured amino acids .</ ref > where R is an organic substituent known as a " side-chain "); often the term " amino acid " is used to refer specifically to these.

For example the standard glutamic acid ( glutamate ) and the non-standard gamma-amino acid gamma-amino-butyric acid ( GABA ) are respectively the brain's main excitatory and inhibitory neurotransmitters, hydroxyproline-a major component of the connective tissue collagen-is synthesised from proline, the standard amino acid glycine is used to synthesise porphyrins used in red blood cells, and the non-standard carnitine is used in lipid transport.

In some amino acids, the amine group is attached to the β or γ-carbon, and these are therefore referred to as beta or gamma amino acids.

The side-chain can make an amino acid a weak acid or a weak base, and a hydrophile if the side-chain is polar or a hydrophobe if it is nonpolar.

Proline is the only proteinogenic amino acid whose side-group links to the α-amino group and, thus, is also the only proteinogenic amino acid containing a secondary amine at this position.

In chemical terms, proline is, therefore, an imino acid, since it lacks a primary amino group, although it is still classed as an amino acid in the current biochemical nomenclature, and may also be called an " N-alkylated alpha-amino acid ".

The and convention for amino acid configuration refers not to the optical activity of the amino acid itself, but rather to the optical activity of the isomer of glyceraldehyde from which that amino acid can, in theory, be synthesized (- glyceraldehyde is dextrorotary ;-glyceraldehyde is levorotatory ).

In addition, the iodoamino acid formed in largest quantity in the intact thyroid is di-iodotyrosine.

The polyester urethane foam is generally produced with adipic acid polyesters ; ;

If a red Bordeaux of a good name and year is bitter or acid, or cloying and muddy-tasting, leave it alone for a while.

In some species, urea is further converted into uric acid.

An acid ( from the Latin acidus / acēre meaning sour ) is a substance which reacts with a base.

The Brønsted-Lowry definition is an expansion: an acid is a substance which can act as a proton donor.

An Arrhenius acid is a substance that increases the concentration of the hydronium ion, H < sub > 3 </ sub > O < sup >+</ sup >, when dissolved in water.

A Brønsted-Lowry acid ( or simply Brønsted acid ) is a species that donates a proton to a Brønsted-Lowry base.

As with the acetic acid reactions, both definitions work for the first example, where water is the solvent and hydronium ion is formed.

A Lewis acid is a species that accepts a pair of electrons from another species ; in other words, it is an electron pair acceptor.

BF < sub > 3 </ sub > is a Lewis acid because it accepts the electron pair from fluoride.

A proton is transferred from an unspecified Brønsted acid to ammonia, a Brønsted base ; alternatively, ammonia acts as a Lewis base and transfers a lone pair of electrons to form a bond with a hydrogen ion.

The species that gains the electron pair is the Lewis acid ; for example, the oxygen atom in H < sub > 3 </ sub > O < sup >+</ sup > gains a pair of electrons when one of the H — O bonds is broken and the electrons shared in the bond become localized on oxygen.

The Brønsted-Lowry definition is the most widely used definition ; unless otherwise specified acid-base reactions are assumed to involve the transfer of a proton ( H < sup >+</ sup >) from an acid to a base.

Reactions of acids are often generalized in the form HA H < sup >+</ sup > + A < sup >−</ sup >, where HA represents the acid and A < sup >−</ sup > is the conjugate base.

The acid dissociation constant K < sub > a </ sub > is generally used in the context of acid-base reactions.

The numerical value of K < sub > a </ sub > is equal to the concentration of the products divided by the concentration of the reactants, where the reactant is the acid ( HA ) and the products are the conjugate base and H < sup >+</ sup >.

The prefix " hydro -" is added only if the acid is made up of just hydrogen and one other element.

In addition to the authentication and acknowledgment procedures which precede and follow the sending of the go messages, again in special codes, each message also contains an `` internal authenticator '', another specific signal to convince the recipient that he is getting the real thing.

Each mode is believed to have a specific attribute -- one inducing pleasure, another generosity, another love, and so on, to include all of the emotions.

Yet his concern even here is with a slowly changing socio-economic order in general, and he never deals with such specific aspects of this change as the urban and industrial impact.

The specific analogy to the dilemma of love is the problem of the `` breakthrough '' in the realm of art.

Let us not confuse the issue by labeling the objective or the method `` psychoanalytic '', for this is a well established term of art for the specific ideas and procedures initiated by Sigmund Freud and his followers for the study and treatment of disordered personalities.

The symposium provides an opportunity to confront the self with specific statements which were made at particular times by identifiable communicators who were addressing definite audiences -- and throughout several hundred pages everyone is talking about the same key symbol of identification.

Even in such technical curricula as engineering, the senior is much more likely than the freshman to choose, as an ideal, liberal education over specific vocational preparation.

There is impressive consistency between specific occupational preferences and the student's basic conception of what is for him a good way of life.

When their faith in civil liberties is tested against strong pressures of social expediency in specific issues, e.g., suppression of `` dangerous ideas '', many waver and give in.

But in ways more fundamental than specific political opinions they are still what they always were: passionate, sure without a shadow of doubt of whatever it is that they are sure of, capable of seeing black and white only and, therefore, committed to the logical extreme of whatever it is they are temporarily committed to.

One specific example is a secret `` fraternity '' which will `` coordinate anti-Communist efforts ''.

There is room for disagreement concerning some of Dr. Conant's specific views.

Among the specific areas of concentration in which the staff is engaged, are such projects as biological and biochemical studies of the effects of microwaves ; ;

Mr. Claude is a specialist in torso development and he has long favored the now-famous Weider Push-Pull Super-Set technique in which one exercise of the Super-Set is a pressing or `` pushing '' movement which accents one sector of a muscle group in a specific way, followed by a `` pulling '' exercise which works the opposing sector of the same muscle group.

A mathematical formula is nothing more than a pattern for solving a specific problem.

We divided the country into five regions plus Hawaii and Alaska and in each is included a general description of the area plus specific recommendations of places and events to cover.

Foliage is the outstanding photo subject in many of the Southern locales mentioned above and some specific tips on how and where to shoot it are in order.

It is for this reason that Roy avoids selecting subjects that require specific recognition of place for their enjoyment.

If no specific organization plan exists limiting the number of scientists at each salary level, the result is a department top-heavy with high-level, high-salaried personnel ''.

Quite naturally, there is a greater availability of those models which are manufactured within a specific country.

The behavior of a biological aerosol, on a much smaller scale, is illustrated by a specific field trial conducted with a non-pathogenic organism.

A solid immunity is the one effective circumstance whereby attack by a specific agent can be neutralized.