zwitterion

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Related to Ampholytes: isoelectric point, zwitterion

ion

 [i´on]
an atom or group of atoms having a positive (cation) or negative (anion) electric charge by virtue of having gained or lost an electron; substances forming ions are called electrolytes. adj., adj ion´ic.
dipolar ion an ion that has both positive and negative regions of charge.
hydrogen ion the positively charged hydrogen atom (H+), which is the positive ion of all acids. See also hydrogen ion concentration.
hydroxyl ion the negatively charged group, OH, present to excess in alkaline solutions.
Zwitterionclick for a larger image
Fig. 318 Zwitterion . Molecular structure of (a) undissociated amino acid, (b) Zwitterion.

zwitterion

the chemical form of an AMINO ACID with a dipolar ion state. The pH at which the amino acid exists as a zwitterion is called its ISOELECTRIC POINT and at this pH it will not migrate in an electric field, produced, for example, by ELECTROPHORESIS.
References in periodicals archive ?
we can assert that synthesized polymeric ampholyte contains in the structure except amino groups also phosphate groups.
The stock solution of acrylamide was prepared by mixing 30% acrylamide powder with 5.2% bis acrylamide, 10% NP-40, 10% CHAPS, 10% APS, 20mM NaOH as catholyte, 0.01[micro]M ortho phosphoric acid as anolyte, 8M urea and 250[micro]l of ampholyte as sample overlay.
The isoelectric focusing of proteins can be determined using immobilized pH gradients or ampholytes. In general, the pH gradient used for protein separation is in the range of pH 3-12.
After cooling to room temperature, samples were diluted with a solution containing 8 M urea, 4% CHAPS, 1% DTT, and 0.4% carrier ampholytes and subjected to further sonication passages followed by 2-DE.
The protein solution was mixed with 0.45% (by volume) pH 2-4 ampholytes, 0.45% (by volume) pH 9-11 ampholytes, and 0.9% (by volume) pH 3-10 ampholytes (SERVALYT[R], SERVA).
First-dimension isoelectric focusing was run on 4.1 g [L.sup.-1] acrylamide tube gel containing 9.5 M urea, 20 mL [L.sup.-1] Triton X-100, 5 mM (3[(3-cholamidopropyl) dimethylammonio]-1-propane-sulphonate), and 20 mL [L.sup.-1] Millipore 2D optimized carrier ampholytes (pH 3-10).
First, members of the Dpfp1 family have acidic isoelectric points ranging from 5.3 to 6.5; marine byssal precursors, in contrast, are highly basic - many with pIs exceeding the effective resolving range of available ampholytes. Second, dreissenid byssal precursors, including Dpfp1, are glycosylated with N-acetylgalactosamine O-linked to serine and threonine residues; there is, however, no evidence for glycosylation in byssal proteins from any marine taxa.
Baker), 2% IGEPAL (Sigma-Aldrich), and 0.25% carrier ampholytes (Bio-Rad).
In vitro-labeled samples were focused with wide range ampholytes (pH = 3-10; Bio-Lyte 3/10, Bio-Rad) in 4 M urea and 10% NP-40, and size-fractionated on 10% sodium-dodecyl-sulfate poly-acrylamide gels (SDS-PAGE) along with Brome Mosaic Virus (BMV) molecular weight markers (110, 97, 35 and 20 Kd) provided as a control with in vitro translation kits (Promega).
Each solution was then dried by centrifugation under reduced pressure, after which 180 =L of rehydration buffer (7 mol/L urea, 2 mol/L thiourea, 20 g/L CHAPS, 50 mmol dithiothreitol, and 5 mL/L ampholytes, pH 3-10) was added to the dry sample to solubilize and denature the proteins.
Each serum sample (500 [micro]g of protein) was solubilized in 8 mol/L urea, 40 mL/L CHAPS, 40 mmol/L Tris, 2 mL/L Bio-Lyte 3/10 ampholytes (Sequential Extraction Buffer 2; Bio-Rad) with 5 mmol/L tris(2-carboxyethyl)phosphine reducing agent and incubated for 1 h at room temperature.
Many factors (e.g., variability in gel conductivity, quality of carrier ampholytes, and electroendosmosis) make IEF inherently difficult to standardize.