Midterm 1 Solutions - Name Student ID Chem 135 Midterm 1 Spring 2008 l a(8 points A 660 mg sample of an oligomeric protein(MW 132,000 was treated

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Unformatted text preview: Name Student ID # Chem 135 Midterm 1 Spring 2008 l. a) (8 points) A 660 mg sample of an oligomeric protein '(MW 132,000) was treated with an excess of dansyl chloride. The labeled protein was hydrolyzed under acidic conditions, and 7.0 mg of the derivative (MW 350) shown below was isolated from the hydrolysate. N((IH3)2 DANva VAL. iNt: K (TEN!) sozna on What structural information can be inferred from the results of this experiment? c. Yi® 5: 6&0 ‘6’5mfififiyom ®/t"31‘omwe 1‘- Sr 0 "it it? wwthi} ~54} 1.6% \D M DEA“! (3 Vi DEV r mobsvocémv /‘k$~wébsv)(ma§tt>gv/3 56%9“) I . I; _\ \ /’l m g ,m "\ ~ i“ ’5- ' m A dr> <Z=O%\OJNM‘VSV)/(‘Snt3;ctu two-Qi‘j) :2: wwmvsv/Wm N~ Gwa- lrl 34.2.».an W F6 Ul‘l VWQl/L r (WWW (ALL MWbai. E ACH MQLE ago/)1 fixfi, cmwim Four: Poms PEPTWEDES. Mug-n wwm N'"TEKMINAL VALiNE, b) (7 points) The volume of a typical bacterial cells is 1.0 ym3. How many hydronium ions does such a cell contain if the interior pH is 7.0? What does your result indicate about the common notion that the multiple charged groups displayed on the thousands of macromolecules in the cell are continually bathed in H3O+ and OH’ ions? (NAV is 6.02 x 1023) .3 H (a v m / s 1. ' 3 "-L "s 5/ ' EELL~ he},th (.0 mix/pom) (“SUM/M (’ /to gm .3 LOX if; L, A . Q. ~ .‘w _ ~‘7 Charmer [Hsm@:l= LCM—(bl: IBO‘MU 'WWQ/L‘ Cal mun P“ m" mmwm» H394 6;) L'wa 9 Ha “ cm W Irv—‘1» % I ml A ‘S _ as ‘ y m": t “p I ‘ .z , A (the at. it: ,,i¢//w19.\)(uexto «\«fic/yl)lta~aéx to /w7»4€ S bQ/ (4,810, f 7%; ,5}.de rimkg Mal—45'" “Dull” jaw; MMA%ML& a; . ,r h i ,r i\ , c) i, awn H3 {9 Err .W Chem 135 Midterm 1 Spring 2008 Page 2 2. a) (1019017115) Bicine (N,N—bi5(2«hydroxyethyl)glycine) is an amino acid derivative that is commonly used to prepare physiological buffers. It is a diprotic acid with AM F 0‘1“ ‘ R “Ms pKa values of 2.30 and 8.30. You wish to prepare 40.0 mM pH 7.50 bicine buffer. erase c: can : RN“; The reagents available are 0.100 M bicine solution at the isoelectric pH of bicine, 0.100 M HCl, and 0.100 M NaOH. Describe the preparation of 1.00 L of the desired buffer. r ‘ x ‘i p Y A , I " fl "' i v, “ v _ M . i_, a, flue» a TDI-(IJME), Wiggcya.oé/i}iulwawmw§L&Mflw Wart-b :7: x i a _ . x r t r, -~ «: ououmww L. .- 40. o m M BlaiNE “kw; at TDt N. w»me c5 W X mum; \ ‘ I , " ‘T_~ ., a . NOTE «(Bx/04L {+£30an DiiOQM alum: waMCw/dbamm 3% a e _. I? " :hmw n ‘ W hzuvifi‘r‘e :7” SO 50 q“ Q93QH1~WJHRNHS>3 at? L 6L); [1 aNfla RNH "' a ' ~ r: .. ” i w o. v “Mag 0 derived”? i tag WEN“? amigo; v—L .. . a .. _ c— - ,7 . . ~~ 2 ~ *1 ~ (“5% we '1? flfiNHée: CLOBWS wwfi.) nKNHL— 0.00J5wi 3? 0.00b5ane5 RNst M M W 34131? in ch 1%” 2 ENE, .(Lp’haig‘vm 0% (Sh/wk. Rh VLWVVbb “bk H “3) ’1' fig N CH" ‘ “flail Wiwu S5“‘"‘L “23 Unit-90 (“'1 “Hub H a. J , . . .1 HOOmL. OglOO M 'Fpieiwti (:axfigwflél truths, 5E" DoiClS‘MNaxDH I await Ls» :L .06 L time a: H20 i b) (5 points) The Ka of lactic acid is 1.38 x 10—4. Determine the concentration of lactate (the conjugate base of lactic acid) in blood (pH 7.4) if the lactic acid concentration in blood is measured to be 1.5 prM. k’mfich/hpdcici\: l-S'iS/xtc {K at: ,6 E “r h m t he will -=s> 3M2; Ital l ==e> ; ~ ”“ “ \2 . v- :, ; t k , — Jw_ VJ, rgl (Newemawamwag’lu fi‘kiw.mvmv ma Ll} \ 1‘ "all; g ‘- - “z; a}; ,. A. I, - fiWfi'th— 2244143- }W Cg w Mam flaws/m 1 W {J fi«%, ' 2: W M i 5 L Chem 135 a) b) Midterm 1 Spring 2008 Page 3 (8 points) Draw the structure of the pentapeptide KNAVE in an ionization state consistent with physiological pH (7.0). 1‘23 / v/ o LNHZ G} o i ‘3‘ “9 ‘5 H N l x, N» K r 5 A? .( \f/l :7: 1/ H C) Q U“) ice-Yaw (7 points) Estimate the isoelectric point of KNAVE making use of the information that the pKa values of the N—terminal amino group, the C-terminal carboxyl group. and the side chains of the lys and glu are 7.83, 3.l5, 10.54, and 4.07, respectively. E 3,; 5 L." 1‘]; . , t 6:23 we “ . ~ ‘ 1.63 (3} m but “min.” 5% P: z (A 07*7.€'—$>/1 : meta/7;; sis;qu Chem 135 Midterm 1 Spring 2008 Page 4 4. (20 points) Match the letter designations of the structures/symbols/terms with the descriptor statements below. HO 0 H, NH2(CH3) 9 SO HO Hsp90 W 3 P50 (A) (B) (C) (D) H\ CH3 9 H‘N 09 S O N as /‘ \ , Ad CHs Hsp 10 we — via/(vi A v0) (E) (F) (G) (H) NH2 N‘ I <: PiPl’O ( NW ampholytes H H (l) (J) F A derivative produced from an oligopeptide fragment that has an N-terminal ala H A function that measures the relative mobility of a protein on a size exclusion column A reagent that can be used to sequence a cDNA molecule by the chain termination method Cl A solid support that can be used to fractionate a mixture of proteins maintained at a pH C below the pl values of the components E An amino acid derivative used as a methylating agent in biosynthesis E) The most abundant protein in eukaryotic cells I A family of molecules with a well—defined range of isoelectric points 1) The partial pressure of 02 at which an oxygen binding protein is half—saturated A signaling molecule that changes intracellular physiology by binding to a [3— A adrenergic receptor on the extracellular sulface of a plasma membrane A eukaryotic chaperonin used in heptameric form as the cap of the barrel that provides CI an isolated microenvironment for folding Chem 135 Midterm 1 Spring 2008 Page 5 5. a) (6 points) Explain how it is possible for a purified protein to have its molecular weight measured as 90,000 using size exclusion chromatography, yet measured as 60,000 using SDS—PAGE in the presence of 2—mercaptoethanol. Which of the measured molecular weights is more reliable? rt . ., 4. ‘. M“ p . ‘ I ... ; “M‘Mm‘mwuab \f Up, J i"\ (kg V U L» w s i D N «Wm huarfiLfiL (suamawayuwwu (K v Q , ‘m I 6 ‘0‘; -— PA CHE :w'wmwmss hm“, M \AI W E: emu—i). in MWL‘“ “Q WM, m Jlde/RLZKJCJ— (1% m. .IWALs-ij . :9 “Talks. renewed“; wimxgtfl was”? a A MUM} VWAMZLc-eiwk .mrmmuxg 3355* PACT: .219!» t b) (6 points) The salt~loving bacterium Halo/oaclerium halobium produces the membrane protein bacteriorhodopsin (MW 26,000) that acts as a light~activated proton pump. X—Ray diffraction studies indicate that the protein contains seven oc—helical segments that span the 45 A thick plasma membrane. Calculate the minimum number of amino acid residues contained in the membrane spanning helices and explain why this number is a minimum. (An MEbeQi‘xNE (it—helix is a 3.613 helix with a 1.5 A rise.) 4 alt ‘MJLML (HgAa Lis Air/'LMJLX m- 30 ataxia. Jam-awn flue, H ‘3 viva». -,Ut~b «at - mew . flamers W 5’5- “ E N W1 e , “7 ‘7‘ '5 m, 2.\ O (L Q cues. JMJW’I—HL , M7 im an... M..WWMWW Min/{fa GMMALM\M\WA, flpoti «chsub «we; MQELM AL (‘ywwflwuimdmg "to THE ’M ‘PLAM'E- ‘, Awa CIWMQg/QL wwmeek “maize-A55 "Tue N97“ 3 Wm flag?) I (Mitzi Av S) w flier. wwwuibw~ #3 ca Guia— wrkmiwrk c) (8 points) The adjacent Table shows the Species pKal ' pKaZ I measured pKa values of ala and ala oligomers. ala 2.34 } 9.69 Explain the reason for the increases in the pKa alaz ' 3.12 8.30 values of the C—terminal carboxyl groups and the ala3 3.39 8.03 decrease in the pKa values of the protonated No Alan, n z 6 3.42 7.94 terminal amino groups. “Tad. Maw:me 0‘3 new, GM: Maw L Carma"? 3w» rewrwubk “fitw‘r‘h’i “W” ymvwvw mealtime-e ghee “crecfiw »V semicwa W ESTAE L E's iii/«‘sz J‘Wa’d‘ibr’wfi C‘M‘M’iw‘fl' ‘ ’ “a” a i~ .r. a} .LMM¢M~;M«/v s N M\ (I; m“ “3 336ch (3., fu‘eafwrvu (W* (W'\% ~ “Tiger, 0g “(3‘3 C}?— ‘ i N GALE A“; i) (mtg ii, ) “with fire/ac \Mvflzwm‘fl .ti my“:ch c.1349.» 0w... as. 4?) Qua £3,245 “ jigs“): “It 5 M a)“ a Taupe emu, 'Dt M V Ni s. M» D 0.4L, Mug/us. duck l a r ' .w a" A N, I W whys-“X Chem 135 Midterm 1 Spring 2008 Page 6 6. a) (7190mm) An oligopeptide (I) produced two fragments (A and B) upon treatment with 2—mercaptoetl1anol. The fragment sequences were A: AVCRTGCKNFL and B: YKCFRHTKCS Treatment ofl with trypsin produce five fragments (i—v) with the following compositions: i: (A, C2, R, S, V) ii: (C2, F, G, K, R, T) iii: (F, L, N) iv: (H, K, T) v: (K, Y) Write down the sequence of I indicating explicitly the positions of the disulfides. Ar'Ve‘C'” RM “("«Ciwcw K “‘N—F..—L_ L...“ s; --- s f; a 5... ., ..___, l . “Y—Km cw Ffw R~~\—l«"i‘~ «flcr‘s b) (8 points) In an attempt to sequence the light chain of a protease inhibitor from the Brassica nigra plant, the polypeptide was fragmented with both chymotrypsin and trypsin. The following fragment sequences were obtained. Chymotrypsin: i: LHKQANQSGGGPS ii: QQAQHLRACQQW iii: RIPKCRKF Trypsin: i: R ii: ACQQWLHK iii: CR iv: QANQSGGGPS v: FQQAQHLR vi: IPK vii: K Write down the sequence of the protease inhibitor light chain providing the reasoning that led to your answer. “TQM, CHYNCTRYPTK Jalfiaa-a—Wwflm, q- LL Qua, (we Cv‘ }C&)\JVMM& d i cmfizxa N57 XJL’M’WMWLWLLA “313‘, mm. wmm Ia; ‘ we. t, E‘X‘W’ ‘ ' r ’\ GS % moses" RN CH ‘2’ M array P‘TXC WWW/M; (Liza) Wear: M w. mfiwml 35%“ mom «3 NH” NJ TH W Wt“ ‘5 r“ *3: {a Emilia Q q, we cV “HEN: PTH: Jim—M {LFLWQAJW ii l -% 5‘4CQU‘ENC’E : . a q .. 3:? KELQEKEF QQAQHLREA C egcowlL. HK‘EQANQ 1 i it; QGVS ...
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Midterm 1 Solutions - Name Student ID Chem 135 Midterm 1 Spring 2008 l a(8 points A 660 mg sample of an oligomeric protein(MW 132,000 was treated

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