One method for separating polypeptides makes use of their different solubilities. The solubility of large polypeptides in water depends on the relative polarity of their R groups, particularly on the number of ionized groups: the more ionized groups there are, the more soluble the polypeptide. Which of each pair of polypeptides that follow is more soluble at the indicated pH?(a) (Gly)20 or (Glu)20 at pH 7.0(b) (Lys–Ala)3 or (Phe–Met)3 at pH 7.0(c) (Ala–Ser–Gly)5 or (Asn–Ser–His)5 at pH 6.0(d) (Ala–Asp–Gly)5 or (Asn–Ser–His)5 at pH 3.0

b) It's said that secondary structures form because of intra- and intermolecular hydrogen bonding involving the peptide bond. Describe what is going on to further stabilize secondary structure through these interactions.

For each of the following chemicals, name the general class they belong to, discuss their solubility in water and explain why they are/are not soluble in water: a) CH3(CH2)26COOH b) KCl c) CH3

Can you please explain how to solve this problem?

The following proteins were separated by SDS-PAGE in the presence of mercaptoethanol. Sketch the relative positions of the various polypeptides on the gel. Label the positive and negative ends of the gel.Protein A: 40 kDa single polypeptideProtein B: 80 kDa protein, made up of two subunits of molecular weight 20 kDa and 60 kDa, held together by noncovalent interactionsProtein C: 200 kDa protein, made up of four identical subunits (50 kDa each) linked together by disulfide bonds

The peptide aspartyl-glutamyl-leucyl-threonyl-alanine, shown in the sketch drawing window, has several ionizable groups. Adjust the charges to show the molecule as it would exist at pH 5.00. Use the pk values in the table below. pK, Values for Ionizable Groups of Amino Acids. Amino Acid pA, of a-COOH pA, of e-NH, pA, of Side Chain Isoelectric Point (pI) Alanine 235 9.87 6.11 Arginine 2.01 9.04 12.48 10.76 Asparagine 2.02 8.80 5.41 Aspartic acid 210 9.82 3.86 298 Cysteine 2.05 10.25 8.00 5.02 Glutzmic acid 2.10 9.47 4.07 3.08 Glutamine 217 9.13 5.65 Glycine 235 9.78 6.06 Histidine 7.11 9.18 6.10 7.64 Isoleucine 232 9.76 6.04 Leucine 233 9.74 6.04 Lysine 218 8.95 10.53 9.74 Methionine 2 28 9.21 5.74 Phenylalanine 2 58 9.24 5.91 Proline 2.00 10.60 6.30 Serine 221 9.15 5.68 Threonine 2.09 9.10 5.60 Trуptophan 238 9.39 5.88 Tyrosine 2 20 9.11 10.07 5.63 Valine 2 29 9.72 6.00 • Use the wedge hash bond tools to indicate stereochemistry where it exists. • If a group is 2chiral, do not use…

b) The likelihood of both triglycerides and phospholipids to behave as liquids at a given temperature is affected by their degree of saturation. Explain what saturation is and provide a biochemical explanation for why it affects the likelihood of a lipid to behave as a liquid at a given temperature. 5) a) Proteins have multiple "levels" of structural complexity. Match the type of chemical bond on the left with the level of protein structure that they are specifically involved in maintaining on the right. (Note that more than one letter may apply to each structural level and that each letter may be used more than once or not at all). a. disulphide bonds Tertiary structure b. hydrogen bonds Primary structure c. ionic bonds Quaternary structure d. peptide bonds Secondary structure