Mid Term 1 & 2-Fall 03 - Name Soc.S ec.# C hem 1 35 l....

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Chem 135 l. a) Name Soc. Sec. # Midterm 1 (8 points) Draw the structure of the pentapeptide DREAM state consistent with physiological pH. Fall2003 in an ionization H,N @, o Y2x ttz rn* 1l o \r*fLt Dlr{ cop t- *, -^frf"" (7 points) Oxytocin is a nonapeptide hormone involved in the milk-releasing response in lactatirrg rnammals. The sequence of a synthetic version of oxytocin is shown below. Calculate the isoelectric point of oxytocin assuming a value of 8.5 for the pKu of the N-terminal amino group, and standard values for the pK^'S of the amino acid side chains. (Note that the C-terminal of oxytocin is amidated.) cFIENqPHG-co2NH2 Lr_rJ T0.4 *$-^rl- ^\.LL-F<i*i{, ?Kor,t O 61rJr g. 5 (;r-.tr,.*u*^.o.g cr."* ^a5.f ) , O.O ( l" ,o ;& ".hil- ) o-,,A tq . , (- 1&- A*6L4 "!.-.{.* ) T&*- l*^o% '*. ." - ,$vl^"oJ4A +€+^-. Q.,o-u . . @ *.-aa @ q'r HrA + @o "t*>A T tJP" u b) H,AO 5.D _--r \a- =+, @5 ^' t *'.;ln +.r-*''^ ". a5 -\d4.-J-J. cifz *,l- 't\^,-.r- a:t ]r-t-
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Ch:m 135 Midterm I Fall 2003 PageZ r (lo L \ + 2' Il,::ltl" acid gly-cine is often used to buffer reacrions occurring in alkaline solutions D' taking advantage of the ionization of the protonated form of the d-amino group. - -- a) (8 points) Calculate the fraction of glycine_containing an unprotonated amino group in a 0.10 M buffer solution w-ith a pH of 9.2. Q ''- -'-- T&t ?Y"- * ,t!* o( o*u. .rr-- n,.-,^{- fi *; q.S =+ 't6\c l" T'' n.z = e,B + ar? =P fcHr.r.l: o.Zs ISH.: oR -o.(o =h();lF|l]=- =o.Zs fnKa31 CcPxa: = + fcuual +3 R r.rut Iers.l/(r*rurl*gSu.l) z f ew rr.l/(r**u.r k te^rHjl ) t gx Hrl / s rry"p { :e Zo nNHz t,/ -i-r .) /./ b) (.7 points) what volume of 5.0 M KoH musr be added ro 1.0 L of the buffer described in (a) in order to raise the pH to l0.O? 5*- (t^"url tu9".r ) = o. io 11 ',,hd @ ph{ q.z zo?,tarl3.r t^t s\ *Ma^- ff j^-:t!,{ }.FJr-r, ry* , z9,t^.- o-,,'- (o zo)(o.ro '^dq) 4 R srua .^^.4 Co.e"Xo'rot^,.t) g eR*a ),*- =^r- .G.^ -d ry$.^- .*,:$. ..- gH +, @ ?H q. Z ,S.r^ec.l"e 6. ozo h,.te R'FJlla .'A o.o8o,, ",Q- RRt ,,"^- dt^ Up->." ,.*I,.od1<fu"* cfi f or-f ;--t^. IS'4- !,*j&^ , & ,'.r;:A-r*-'n '-^ RNtl3 OHU *----*9' RFJHZ + rl 2c a'cc.r-r*a C..,r"!-c- JO.a! Ar-"-or' @rHro.b/ to.c: cl.9+aT( b z= 9""1 ( ;*,.\rr.^. . cu^! &d.r^ Cl t'r o* v'^.4.-o- => L-A (t"*u. / tffi*, = o .L t' (^on *, / na$,. .r) = t'st> => ne$,.ir= t'59ttR*r 't z.5g ^r.F*r= o'lo r^.Q ^o : o'o3q ""-*{* + tEi'= nr,.r.rl-lr. O. 06l h*4. f-0^t nr-r*0^" 4 a$.- o.i.d;.tr;"\ tf, f Or-i k-€,4-i0.r- .-c-*-e,ro--. "t o.oqr.^arc "d r<Rulr.r+r-o- RNI-{z, Y o oqt ".^*t a* Kos .*:,*' q^*.*}11_* D cL.r,^.,r1. t"cu1 te <ov/,"^.r/"r"r)=lj_T::_: tcyrr<o,., qr- s 1-,_{scrr
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Chem 135 Midterm I Fail 2003 Page 3 3. (15 points) A decapeptide (I) recently isolated from a variety of African thistles has been shown to have anticancer properties. Determine the sequenCe of the decapeptide from the experimental observations listed below, providing the reasoning that led [o your conclusions. i) One cycle of Edman degradation yields 2 mol of PTH-asp per mole of I. ii) Treatment of I with 2-mercaptoethanol followed by trypsin produces three peptides with the following composition: A(ala, cys, phe), B(arg, asp), C(asp, cys, gly, met, phe) iii) of A yields pTH-cys. iv) Treatment of I with carboxypeptidase Y produces 2 mol of phe per mole of I. v) Treatment of C with cyanogen bromide produces two peptides with the following composition: D(asp,met*), E(cys, gly, phe) (metx: methionine is converted to homoserine lactone) vi) of E yields pTH-gly.
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This note was uploaded on 02/27/2011 for the course CHEM 135 taught by Professor Peternemes during the Spring '11 term at San Jose State University .

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Mid Term 1 & 2-Fall 03 - Name Soc.S ec.# C hem 1 35 l....

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