Ch4-120130 - CHEM 350: Introduction to Biological Chemistry...

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Unformatted text preview: CHEM 350: Introduction to Biological Chemistry Brian Lee, Ph.D. [email protected] Office: Neckers 146G or 324 Phone: 453-7186 Hours: 9:30am to 10:30am or by appointment Website: https:/ / Textbook (required, U.S. edition only) Fundamentals of Biochemistry, 3rd Ed., Voet, Voet & Pratt. Study Guide (recommended) Student Companion to Fundamentals of Biochemistry, 3rd Ed. Help Desk Tuesday 6:30 to 7:30 pm in Neckers 218 Thursday 5:00 to 6:00 pm in Neckers 410 Announcements Undergraduate Research Opportunities Research for credit (such as CHEM 396 or CHEM 496) Student worker ($8.00 per hour) ( Undergraduate Assistantships ( McNair Scholars Program ( REACH Awards Competition ( (due Jan 30th) Undergraduate Scholarships (due Jan 31st) Chemistry Majors see Department website Scholarships.pdf Science Majors see College of Science website Summer Research Experiences for Undergraduates (REU) Assignments Read Chapter 5 Proteins Chapter 5 Problems • First Midterm Exam, Monday February 6th – Chapters 1 through 5 • Help Desk Tuesday 6:30-7:30pm in Neckers 218 Thursday 5:00-6:00pm in Neckers 410 Peptides also have a characteristic titration curve and pI. Naming Peptides Alanylglutamylglycyllysine or Ala-Glu-Gly-Lys or AEGK Determine the pI 9.87 1 pI = ( pK 2 + pK 3 ) 2 1 = (4.07 + 9.87) = 6.97 2 4.07 pI 2.16 pKa 2.16 4.07 9.87 10.54 low 0 0 + + 10.54 high 0 0 net +2 +1 0 -1 -2 Amino acids with Ionizable Side-Chains (R-groups) 3.90 10.46 4.07 10.54 12.48 6.04 8.37 Stereochemistry Chiral molecules are optically active, meaning they rotate plane polarized light Figure 4-9 chiral center – assymetric center Chirality (Stereochemistry) -mirror image is not superimposible -tetrahedral carbon has four different substituents -mirror image molecules are enantiomers -optical isomers rotate plane polarised light -L (-) for levorotary -D (+) for dextrorotary Fischer Convention for Configuration All 20 common -amino acids are L stereoisomers Cahn Ingold Prelog rules (RS) -assign priority by atomic number -lowest priority points away -rotation from highest priority -left handed (CCW) is S -right handed (CW) is R All amino acids are L All amino acids but one are S Only Cysteine has R chirality Due to Sulfur being higher in priority than Carbon L and S Why is stereochemistry important? Biological systems are stereospecific. Ibuprofen – only one enantiomer is anti-inflammatory Thalidomide – one enantiomer is a mild sedative, the other enantiomer causes birth defects. Thalidomide was often prescribed for morning sickness Modified Amino Acids Hydroxyproline is found in collagen (gelatin) and plant cell walls. Proline permits formation of the collagen triple helix (ch 6). Hydroxylysine is also found in collagen and is used to create covalent cross-links between collagen chains. g-Carboxyglutamate is found in prothrombin. The added carboxylate allows this amino acid to chelate calcium ions. “21st amino acid” UGA stop codon serine on tRNAsec is modified prior to translation. Amino acids found in metabolism. Ornithine is a catalytic intermediate of the urea cycle. Citrulline is generated from ornithine. Neither is incorporated in proteins during translation of mRNA by the ribosome. Citrulline can be generated by deamination of Arginine. collagen signal transduction actin Figure 4-14 thrombin histone neurotransmitter allergic response thyroid hormone Figure 4-15 neurotransmitter Glutathione (GSH) is a tripeptide of Glu-Cys-Gly. Note: Glu is linked by sidechain carboxylate. GSH protects cells from reactive oxygen species which can cause oxidative damage to DNA and proteins Green Fluorescent Protein Nobel Prize in 2008 Martin Chalfie Osamu Shimomura Roger Tsien Modified Tyrosine becomes fluorescent. Absorbs UV light and emits green light. ...
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This note was uploaded on 03/26/2012 for the course CHEM 350 taught by Professor Lee during the Spring '08 term at SIU Carbondale.

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