Extra+practice+problems+for+Midterm+2+solutions

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Unformatted text preview: Professor: Chris Chang GSIs: Stephanie Jones, David Zee Chemistry 103 Extra Problems for Midterm #2 1) Hydrolysis. Matrix Metalloproteinases (MMPs) are involved in remodeling of cell membranes and are connected to inflammation events in cancer, heart disease, and neurodegeneration. a) The active site is shown below for MMP3 with Co metal substituted in the active site. What is the oxidation state and d electron count for the metal center? Glu O Y Co His-N” I .\N-His N-HlS b) The enzyme takes in substrates such as the one below, cleaving peptide bonds after aromatic residues on the C—terminus. Given this specificity, write the overall reaction that MMP3 catalyzes. o 8/ 0 MW} 9/ H2N\)J\u/qO/N%J\IJOH a h . ( HZ~\)k N \/ c) Propose a logical arrow pushing mechanism for this reaction, showing d-electron count and oxidation state for the metal in each step. Abbreviate non-essential groups 0 as R], R2, etc and clearly identify what they ar . H '2," 9"“ ‘14 ‘°‘~ Gl‘k/a .4 9: /’“ R / '\ "' K 0 H H 7'“ R,’LK~’ 1' i H ’ro'l'fl—pll dc e \ 0/ H \ 0 M 0? I __________§ ~91 / _,.__._—————->; Co C C) f’r - / a N “:5 m-,)/ l M-Hu no.” L COOH Nut; H H K 9 — \Q" a 7. 0““ /° “‘ (A N / 1 P T lel/O H I?) u H /[(g _.______—=> 1 2‘ [if-9 c) : ' ‘0 a -' ' ‘ “ /< ., Co / ./ H§S~/ tarot“ 00.75". - u n ‘v . Nah HTS k N- h :3 NIH.) Cd</°® l3 a. ~ GM 0 I" b . t + H (b \é. 1* 0 \ t l 44 K ,H M l O a o o / /b 9 l C 5 z" — K \on N / q” M H ‘ C0 ’1? ’ ‘t ‘1, S h ‘ ‘ :‘N / A A) a is U H\ 5 N H iJ (1) Assuming that the ligands are idealized to have the same bond length, draw a crystal field for the Co(II) MMP3 active site and fill in the electrons. Predict how many ligand field absorption bands one would see in the UV-Vis spectrum and give your reasoning. How many ligand field bands would the Zn(II) form have? 0 CDC Si) <9. 2? 2m (9“ 4-— Gr’ 4’ f1 4%,— fib "(JV ’6 2‘ 4b 4‘7 Q“ ,A-v ’45" z “ +006 LAJS AAA). 4—0 ZUO &-£ (51-2. (Qqu‘un 2) 02 binding. Hemoglobin (Hb) and Myoglobin (Mb) are heme-based proteins that bind and transport 02 in humans and other mammals, giving superoxide adducts. a) Besides Hb/Mb, name the other two proteins (full names, no abbreviations) that perform this function in Nature and list what metals they use [see hints in b) and 0)]. HQewiocxlat/iin (HC-\ 3 Hmtmfir’x/W‘I‘ifl b) Draw the active sites for the Cu-dependent 02 transport protein, before and after 02 binding. Show how 02 interacts with the active site by giving the oxidation state(s) of the metal(s) before and after 02 binding and what form the bound 02 is in. I if 9;? ’ (m— N N, m; an v N N 4,“, \ / P / O \ / htvlaaC-A CM .-~—H.s Hts-N'/Cu\ I CM , N4”) / \ / \ 14:va “'“n 1413’“ C) Mum‘s kt‘potl oz O}. 1. Q41) '2. C4433 c) A mutated form of this 02-binding protein has the following active site with a Ti/Fe core. Given that Ti is in the Ti“ oxidation state, what is the oxidation state and d electron count of the Fe in this active site? a 73+ 6 His-N, / \ ,N-His ) 6Q / I; F \ His-N 1' /5e N-His 0&2; Asp d) Predict how 02 will bind to this active site, based on principles of natural Oz'binding enzymes, by drawing the chemical structure for 02 in the bound form. Give the oxidation state, (1 electron count for each metal, and name the 02 binding mode. 3) Electrochemistry. [Cu(CN)4]2' and [Cu(His)4]2+ are isostructural complexes that have square planar geometries. a) Draw the crystal fields for these two complexes and fill in the d electrons. What are their oxidation states? g t 1"“: 1 I r ::“"3 ‘ v 1):! t 1 Lawn . a m [We q «H» — 43a finicmrm “elf CMCED b) Which will be easier to oxidize? Please provide brief reasoning. I. [Cu(c"°)‘|1 is ustu 'l-o oxhlimz ELCAQJL ’l'bu. LII—~11 owytst'xk (HOMO) n EA— , c) Below is the cyclic voltammogram of [Cu(CN)4]2'. Draw the cyclic voltammogram of [Cu(His)4]2+ on the same plot. Current / pA Potential / mV M 1m «th’ M” “1 chn'D/CJI) Gow?\Q—§_ ...
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