Oxytocin, a hormone peptide of nine amino acids, is widely used in obstetrics to induce uterine contractions. There is an intramolecular disulfide bond which must be reduced before sequencing. Reduced oxytocin has the composition Asn 2Cys Gln Gly Ile Leu Pro Tyr . Partial hydrolysis of reduced oxytocin led to the following fragments: (a) AsnCys (b) CysTyr (c) TyrIleGln (d) CysProLeu (e) IleGln (f) LeuGly (g) GlnAsnCys . Reaction of reduced oxytocin with carboxypeptidase showed glycine as the first liberated amino acid. What is the amino acid sequence of oxytocin?

Which of the peptide sequences below best matches the hydropathy plot shown? L 10 Residue Number 4 2 Hydropathy value -2 0 セー RAFLILFMTYFLILFLI ILYYAGSREDHSGYLIL OLHGDQNRERDGHSQERD EQSDTERNQHGALIYLI 01 5 15

Determine the sequence of the following 10-mer of ferritin using the data below. i. Complete acid hydrolysis of the 10-mer results in identification of 1A, 1D, 1E, 1F, 1H, 1K, 2L, 1T, 1Y ii. Digestion of the 10-mer with chymotrypsin results in 3 fragments containing (D, H, K, T), (F, L) and (A, E, L, Y) iii. Digestion of the 10-mer with V8 protease, which cuts on the C-side of acidic amino acids, results in three fragments containing (D, F, L, Y), (A, E, L) and (H, K, T) iv. Digestion with trypsin results in a fragment H-T and a fragment with all the other amino acids v. Treatment of the 10-mer with FDNB followed by complete acid hydrolysis results in the following two derivatives, DNP-1 and DNP-2 vi. Treatment of the 10-mer with a carboxypeptidase results in a free threonine

You are working at a major pharmaceutical company, and you have purified an engineered enzyme, and you need to determine the protein stability (kJ/mol). Accordingly, you have collected equilibrium unfolding data using the chemical denaturant urea at 20°C, pH 7.5 and I atmosphere using fluorescence spectroscopy. a) Determine the protein stability (AG [kJ/mol]) via nonlinear least squares (using the available data). b) Write the partial differential equation (i.e., general functional form, variable, constants). c) Describe what would happen to the isotherm if the temperature was increased to 25 °C. Urea [M] 0 0.25 0.5 0.75 1 1.25 1.5 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 FL 340nm 316 315.5 315 314.5 314 315 300 275 225 125 75 60 55 54 53 52.5 52.25 52 51.75 51.5 dG = Vdp-SdT+μA dnд + μB dng dGp = μA dnA+ μg dng A = Folded State B = Unfolded State

Identify the structure of the predominant form of the pentapeptide at pH = 12 if there is a pentapeptide Ile-Lys-Asp-Phe-Gly

6  (a) A decapeptide has the following amino acid composition: Ala2 , Arg, Cys, Glu, Gly, Leu, Lys, Phe, Val Partial hydrolysis yields the following tripeptides: Cys-Glu-Leu + Gly-Arg-Cys + Leu-Ala-Ala+ Lys-Val-Phe + Val-Phe-Gly. Reaction of the decapeptide with 2,4-dinitrofluorobenzene yields 2,4-dinitrophenylysine. From the experimental data, deduce the primary structure of the decapeptide. (b) Suggest a scheme you will follow to synthesize the dipeptide Ala-Gly

Draw the structure of the tri-peptide Leu-Asn-Ser  at pH 7.4. Use wedges and dashes around the alpha-carbons, and indicate charges where appropriate. Indicate which amino acid(s) has an R group that would avoid water.

This SDS-PAGE loading buffer has SDS (a denaturing detergent), β-mercaptoethanol (a reducing agent), Coomassie Blue (a dye), and glycerol. You will need to dilute your protein samples such that the final concentration of the loading buffer is 1x, meaning that you will add 5 parts of the protein sample for every 1 part of 6x buffer. Calculate how much of the 6x loading buffer you will need to add to each sample. Then, add the appropriate amount of 6x SDS-PAGE loading buffer to the samples. Store the samples in the -20°C freezer. What is the final concentration of glycerol in each of the samples?