The cell surface of the bloodstream form features a dense coat of variable surface glycoproteins ( VSGs ) which is replaced by an equally dense coat of procyclins when the parasite differentiates into the procylic in the tsetse fly midgut.

The tertiary structure of this halo is well conserved between different VSGs ( in spite of wide variation in amino acid sequence ) allowing different VSGs to form the physical barrier required to shield the trypanosome's surface.

All but one of these are ' silent ' VSGs, as each trypanosome expresses only one VSG gene at a time.

This new VSG will likely not be recognised by the specific immune responses raised against previously expressed VSGs.

However, for them to fulfil their shielding function, different VSGs have strongly conserved structural features.

VSGs are made up of a highly variable N terminal domain of around 300 to 350 amino acids, and a more conserved C terminal domain of around 100 amino acids.

The VSG gene archive is the collection of silent VSGs in the T. brucei genome.

However, only 5 % of the archive is made up of such complete silent VSGs.

To utilise the rest of the silent VSG archive, ‘ mosaic ’ VSGs can be formed by replacing part of the expressed VSG with a structurally homologous region from the archive.

This parasite efficiently evades the host animal's immune system through the use of variable surface glycoproteins or VSGs.

These VSGs allow the organism to constantly manipulate and change the surface structure of its proteins, which means it is constantly being presented to the immune system as a new foreign organism and this prevents the body from mounting a large enough immune response to eradicate the disease.

This balance is the proportion of proapoptotic homodimers that form in the outer-membrane of the mitochondrion.

This acidic environment causes a conformational change in the E protein which disassociates it from the prM protein and causes it to form E homodimers.

Different STATs form hetero-or homodimers.

All PDGFs function as secreted, disulphide-linked homodimers, but only PDGFA and B can form functional heterodimers.

Glucosidases then remove terminal glucose residues ; it is believed that this glucose trimming is responsible for the conformational change needed for LPL to form homodimers and become catalytically active.

* Step 1: in the first step of IF assembly two parallel, unstaggered intermediate filament polypeptides chains form a dimer via their a-helical rod domains ; these dimers can be either homodimers or heterodimers.

It has been shown that some members of this family form homodimers.

Hormone-activated estrogen receptors form dimers, and, since the two forms are coexpressed in many cell types, the receptors may form ERα ( αα ) or ERβ ( ββ ) homodimers or ERαβ ( αβ ) heterodimers.

RPB3, RPB5, and RPB7 interact with themselves to form homodimers, and RPB3 and RPB5 together are able to contact all of the other RPB subunits, except RPB9.

The cadherins are a family of transmembrane proteins that form homodimers in a calcium-dependent manner with other cadherin molecules on adjacent cells.

Mike seized a blanket from a pallet in a corner, spread it on the floor and used it to form a bag in which he placed his booty.

By counting the number of stalls and urinals I attempted to form a loose estimate of how many men the hall would hold at one time.

Jury, judge and executioner were riding the range in the form of a single unknown figure that could materialize anywhere, at any time, to dispense an ancient brand of justice the men of the new West had believed long outdated.

Her form was silhouetted and with the strong light I could see the outlines of her body, a body that an artist or anyone else would have admired.

Twenty minutes later she was at the desk of the Grafin's pension, her tears dried, signing a hotel form and asking for a bath.

Dr. Louis Lalaurie examined the inert form of the slave on the parquet dance floor and pronounced him dead.

It had been a very long time that had no form and no end.

( Since the time-span of the nation-state coincides roughly with the separate existence of the United States as an independent entity, it is perhaps natural for Americans to think of the nation as representative of the highest form of order, something permanent and unchanging.

Water, air, fruit, poetry, music, the human form -- these things are important to Persians, and they experience them with an intense and discriminating awareness.

And it is expressed, at least to their taste, in a perfect form.

such a statement would be the rankest form of oversimplification.

The unit of form is determined subjectively: `` the Heart, by the way of the Breath, to the Line ''.

The test of form is fidelity to the experience, a gauge also accepted by the abstract expressionist painters.

Rather than putting their trust in ephemeral sensations they seek form in the stable relationships of pure design, which symbolize an order more real than the disorder of the perceptual world.

But in this approach it is the artist's ultimate insight, rather than his immediate impressions, that gives form to the work.

Some let dances take their form from the experience of creation.

An exploration of these possible relationships constitutes the process of creation and thereby gives form to the dance.

But her conscious need was to break away from constricting patterns of form, a need to let the experience shape itself.

It is through the metamorphosed dancer that the germ of form is discovered.

`` we the People of the United States, in order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common Defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America ''.

`` We the people of the Confederate States, each state acting in its sovereign and independent character, in order to form a permanent federal government, establish justice, insure domestic tranquility, and secure the blessings of liberty to ourselves and our posterity -- invoking the favor and the guidance of Almighty God -- do ordain and establish this Constitution for the Confederate States of America ''.

Then he began to speak about the tension in art between the mess and form.

It realized that to admit them was to jeopardize form.

I granted this might be so, but found the result to be even more attention to form than was the case previously.

If we look at recent art we find it preoccupied with form.