Which of the following terms best describes the side chain of valine? A) acidic
ID: 513491 • Letter: W
Question
Which of the following terms best describes the side chain of valine? A) acidic B) basic C) charged, polar D) uncharged, polar E) nonpolar Which of the following best describes the side chain of arginine at a pH of 11? A) hydrophobic B) nonpolar C) charged and polar D) uncharged but polar E) aprotic Give the pH at which histidine exists in the following form. A)0 4 B) 4 C) 8 D) 12 E) 14 When a disulfide linkage is formed, the compound containing this new linkage has been A) hydrolyzed B) dehydrated C) electrolyzed. D) oxidized. E) reduced. In conventional peptide synthesis, the nitrogen of a given amino acid must be deactivated or blocked while the carboxyl group is activated. Which of the following reagents is used to protect the amino group of an amino acid? A) di-tert-butyl dicarbonate B) dicyclohexylcarbodiimide D) trifluoroacetic acid E) phenylisothiocyanate In peptide synthesis, give the use of dicyclohexylcarbodiimide. A) activates the car group of an amino acid B) protects the carboxyl group of an amino acid C) protects the amino group of an amino acid D) activates the amino group of an amino acid E) removes the protecting group on the N-terminal amino acidExplanation / Answer
1. Which of the following terms best describes the side chain of valine?
A) acidic
B) basic
C) charged, polar
D) uncharged, polar
E) nonpolar-----answer
Non-Polar Side Chains:
valine has side chains which have pure hydrocarbon alkyl groups or aromatic are non-polar.
==============================================
2. Which of the following best describes the side chain of arginine at a pH of 11?
A) hydrophobic
B) nonpolar
C) charged and polar----answer
D) uncharged but polar
E) aprotic
pKa 12.5 > pH 6.0, so the arginine gets a proton = +1 charg3
3. Give the pH at which histidine exists in the following form.
A) 0
B) 4-answer
C) 8
D) 12
E) 14
4. When a disulfide linkage is formed, the compound containing this new linkage has been
A) hydrolyzed.
B) dehydrated.
C) electrolyzed.
D) oxidized.--------------answer
E) reduced.
5. In conventional peptide synthesis, the nitrogen of a given amino acid must be deactivated
or blocked while the carboxyl group is activated. Which of the following reagents is used to
protect the amino group of an amino acid?
A) di-tert-butyl dicarbonate
B) dicyclohexylcarbodiimide-r
C) ninhydrin
D) trifluoroacetic acid ----answer
E) phenylisothiocyanate
6. In peptide synthesis, give the use of dicyclohexylcarbodiimide.
A) activates the carboxyl group of an amino acid-answer
B) protects the carboxyl group of an amino acid
C) protects the amino group of an amino acid
D) activates the amino group of an amino acid
E) removes the protecting group on the N-terminal amino acid
dicyclohexylcarbodiimide.These actuating specialists were initially created. Most basic are dicyclohexylcarbodiimide (DCC) and diisopropylcarbodiimide (DIC). Response with a carboxylic corrosive yields an exceedingly receptive O-acylisourea. Amid simulated protein blend, (for example, Fmoc strong state synthesizers), the C-end is frequently utilized as the connection site on which the amino corrosive monomers are included. To improve the electrophilicity of carboxylate gathering, the adversely charged oxygen should first be "initiated" into a superior leaving gathering. DCC is utilized for this reason. The contrarily charged oxygen will go about as a nucleophile, assaulting the focal carbon in DCC. DCC is incidentally appended to the previous carboxylate gathering (which is presently an ester gathering), making nucleophilic assault by an amino gathering (on the joining amino corrosive) to the previous C-end (carbonyl gathering) more proficient. The issue with carbodiimides is that they are excessively responsive and that they can along these lines cause racemization of the amino corrosive.
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