The amino acid glycine is often used as the main ingredient of a buffer in biochemical experiments. The amino group of glycine, which has a pKa of 9.6, can exist either in the protonated form. (a) In what pH range can glycine be used as an effective buffer due to its amino group? (b) When 99% of the glycine is in its protonated form, what is the numerical relation between the pH of the solution and the pKa of the amino group?

A purified protein fraction has a total sample volume of 450 µL. The sample has a corrected A280 of 0.244, and the blank corrected A280 was 0.077. (Both values were measured with a path length of 1.00 cm.) If 5.50 µL of the sample was used in a reaction, calculate the mass of protein in the reaction (in µg).

Please draw titration curves for peptide HFDTYA and HEKDGQ, and calculate the pl for each. Usethis information to explain why the peptide HFDTYA has low solubility and HEKDGQ has a highersolubility in bulk water at pH = 7.

After staining an SDS-PAGE gel with Coomassie Blue G-250, the protein bands are visualized by de-staining the gel in a Coomassie Blue G-250 de-staining solution. This solution is made up of 10% acetic acid, 50% methanol, and 40% distilled water. How much of each of these components do you need to prepare 5 liters of Coomassie Blue G-250 de-staining solution?

N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid) buffer at pH 7 with 400 mM NaCl. A A purified protein is in a Hepes dialysis membrane tube holds a 5.0 mL sample of the protein solution. The sample tube floats in a beaker containing 0.50 L of the same Hepes buffer, but with 0 mM NaCl, for dialysis. Small molecules and ions (such as Na*, CI", and Hepes) can to diffuse across the dialysis membrane, but the protein cannot. Assume there are no sample volume changes during the dialysis. Calculate the final concentration of NaCl in the protein sample once the dialysis has come to equilibrium. Calculate the final NaCl concentration in the 5.0 mL protein sample after dialysis in 300 mL of the same Hepes buffer, with 0 mM NaCl, twice in succession. [NaCl] after a single dialysis: [NaCl] after a double dialysis: mM mM

A protein has a dissociation equilibrium constant equal to 4.0um. What is the concentration of free ligand when the fraction of bound sites is 0.7

An enzyme uses a lysine and a histidine as general acid-base catalytic residues. In one direction of the reaction, the lysine and histidine residues are typically protonated (~NH3*, ~Im), but in the other direction of the reaction, the two residues are "reverse protonated" (~NH2, ~Hlm*) (see below scheme). A pH profile of the reaction at various pH values yielded estimates of 7.57 and 9.30 for the macroscopic ionization constants pk,' and pK2, respectively. A separate set of experiments with site-speciffic variants of the enzyme yielded an estimate of 8.78 for the microscopic ionization constant pKp. Given this information, what is the value of the microscopic ionization constant pKA? Report your answer to the nearest hundredth. Lys-NH3* His-HIm" KB H KA H* Lys-NH2 Lys-NH3* His-HIm" His-Im Kc H* Kp Lys-NH2 His-Im

A set of biomolecules listed in the table at right are in solution at pH 6.8, when they are passed through the multi-step separation process shown below. The sample passes through an ultrafilter with MWCO of 50,000 (assume this filter gives a perfect separation of molecules above and below the MWCO), and the retentate then flows through an ion exchange column filled with beads that have a positive charge under the operating conditions (pks = 7.3). Inlet Biomolecule Mixture pH 6.8 Ultrafiltration MWCO 50,000 Permeate Retentate lon Exchange Column Biomolecule Molecular weight pl A 68,000 4.2 B 92,600 9.6 C 144,000 A-3. Which biomolecules (A, B, C, etc.) exit the process in the permeate stream? K C-3. Which biomolecules are retained inside the ion exchange column? D E F G H B-3. Which biomolecules exit the process after passing through the ion exchange column? 5,800 68,000 Packed with DEAE cellulose beads, which have positively charged groups below a pH of 7.3 156,000 45,000 16,000 None…

A purified protein fraction has a total sample volume of 360 µL.  The sample has a corrected A280 of 0.484, and the blank corrected A280 was 0.052.  (Both values were measured with a path length of 1.00 cm.)  If 5.00 µL of the sample was used in a reaction, calculate the mass of protein in the reaction (in µg).

In an experiment, what happens to the calculated molar mass after waiting an hour between thawing the frozen cyclohexane and adding the unknown compound, during which time some of the cyclohexane evaporated.   Will the molar mass be too large, too small, or unaffected?  Explain.|