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- W2187625984 abstract "Determination ofthecrystal structure of ethylchlorophyllide a-2H20bysingle crystal x-raydiffrac- tiontechniques hasprovided thefirst detailed molecular structural dataavailable fora magnesium-containing derivative ofchlorophyll. Atthesametimetheaggregation observed inthisstructure serves asthebasisforamodelof chlorophyll aggregation invitroandinvivo.Themag- nesiumatom inethylchlorophyllide isdisplaced 0.4A fromtheplaneofthechlorin ringinthesamedirection as themethylestersubstituent. A watermoleculeoccupies thefifth coordination site. A secondwatermolecule ishy- drogenbondedtothecoordinated watermolecule andalso tothecarbonyl oxygenatomofthemethylester. Hydrogen bondsbetweenthewatermolecules andcarbonyl oxygen atomslinkthechlorophyllide molecules intoatwo-dimen- sional aggregate ofcrosslinked one-dimensional polymers. Therelationship ofthisaggregate toaggregates ofchloro- phyllbothinvitro andinvivoisdiscussed, asistheef- ficiency ofexciton transport withinthepolymer. Prompted bythekeyrole ofchlorophylls inphotosynthetic processes, numerous investigators havestudied thestructure andfunction ofthese pigments bothinvivo andinvitro. The complete synthesis ofchlorophyll abyWoodward (1)crowned anearly sequence ofstructural studies. A vastamountof information hasbeenprovided bytheapplication ofmodern physical techniques. Infrared andmagnetic resonance mea- surements (2, 3)havebeenusedtogreat advantage andx-ray structural investigations (4,5)havebeencarried outon several degradation products. Thesestudies havenot,how- ever, provided anunambiguous modelforthedetailed molec- ularstructure ofchlorophyll oranymagnesium-containing derivative. Asaresult ofvarious studies designed todetermine the nature andenvironment ofchlorophyll inphotosynthetic systems, itisnow widely accepted (6-11) thatchlorophyll aggregates playimportant roles inphotosynthesis. Anearly model ofthechloroplast lamellae (7)envisioned atwo-dimen- sional aggregate ofchlorophyll molecules attheinterface between protein andlipid layers. Thismodelwasbased pri- marily onthesimilarity oftheposition oftheredabsorption maximuminthevisible spectrum ofchlorophyll invivo to thatobserved forchlorophyll aggregates invitro. While chlorophyll invivo mayoccur inavariety ofenvironments and theshifts oftheredabsorption bandmayarise fromcombi- nations ofchlorophyll-protein andchlorophyll-chlo rophyll interactions, recent investigations (8-13) haveprovided convincing evidence fortheexistence ofchlorophyll aggre- gates inseveral types ofphotosynthetic material. Itisclear thatanunderstanding ofthenature ofchlorophyll aggrega- tion isofprime importance inanunderstanding ofthemolecu- larprocesses involved intheinitial stages ofphotosynthesis. Inmostrespects thealkyl chlorophyllidest serve asexcel- lentmodels ofchlorophyll. Visible absorption spectra, nu- clear magnetic resonance spectra andinfrared spectra ofthe chlorophyllides invitro differ little fromthose oftheparent chlorophyll (2,14). Asmight beexpected themostprofound effect oftheabsence ofthephytyl groupisthereduced solubility ofthechlorophyllides inhydrocarbon solvents. Chlorophyllide itself occurs invivo astheimmediate biosyn- thetic precursor ofchlorophyll (15). Schultz andSauer(11) havepresented evidence thataggregated chlorophyllide is present ingreening leaves. Thex-ray structural determination ofethyl chlorophyllide a-2H20reported herein provides thefirst detailed structural dataforamagnesium-containing chlorophyll derivative. In addition, thenature oftheaggregate observed inthis crystal- line derivative provides auseful modelofchlorophyll aggre- gates, bothinvivo andinvitro." @default.
- W2187625984 created "2016-06-24" @default.
- W2187625984 creator A5065222731 @default.
- W2187625984 date "1973-01-01" @default.
- W2187625984 modified "2023-09-27" @default.
- W2187625984 title "TheCrystal andMolecular Structure ofEthylChlorophyllide a*2HO and ItsRelationship totheStructure andAggregation ofChlorophyll a* (exciton migration/photosynthesis)" @default.
- W2187625984 cites W1976359003 @default.
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- W2187625984 hasPublicationYear "1973" @default.
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