The biogeochemistry of tetrapyrrole pigments, emphasizing chlorophyll

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7198209

Louda, J W

Electronic absorption spectra recorded on native geopigments and on in vitro derivatives, obtained with combinations of copper insertion and borohydride reduction reactions, allowed a sensitive chromophore identification' scheme to be developed. Quantitation of the Ni and VO geoporphyrins, as well as the benzo-forms of each, was tested and precisions at the level of 100 [+-] 5% found. An overall methodology for obtaining repeatable low-voltage mass spectra on geoporphyrin arrays is presented. Repeatabilities for the various mass spectral-derived indices were; %DPEP ([+-]2%), X ([+-]2%), A.I.([+-]5%) and % BENZ ([+-]10%). Quantitation of the metallobenzoporphyrins was much better ([+-]2%) with UV/VIS techniques. Tetrapyrrole geochemistry was investigated at all stages of organic evolution. Thus, viable and senescent/dead uni-algal cultures, sediment trap material, surface (<1m) sediments, deep ocean long cores (DSDP), oil shales and petroleum crudes were investigated. Results indicate that the chlorophylls can serve as sources for a variety of geoporphyrins. Early in diagenesis two competing reactions dictate further fossilization.' First is the loss of the carbomethoxy group. This produces pyropheophorbides which can either lead to the true DPEP series, via a sequence of defunctionaliation reactions or, via intramolecular cyclization (dehydration), to certain 13[sup 2], 17[sup 3]-cyclopheophorbide enols. The latter, following defunctionalization, give rise to DiDPEP and/or DPEP-type pigments with a 7-membered exocyclic ring. Second, chlorophyll nuclei which have undergone oxidative scission of the isocyclic ring can, through purpurins and chlorins, theoretically yield C28-C30 ETIO-series porphyrins. Bacteriochlorophyll-a was found to be a dominant pigment in several anoxic sediments and is suggested as an important and highly specific precursor for certain geoporphyrins (i.e 3-methyl-desethyl-DPEP).

• Research Organization: University of South Florida, Tampa, FL (United States)
• OSTI ID: 7198209
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
023000* -- Petroleum-- Properties &amp; Composition
04 OIL SHALES AND TAR SANDS
040500 -- Oil Shales &amp; Tar Sands-- Properties &amp; Composition
58 GEOSCIENCES
580000 -- Geosciences
ABSORPTION SPECTRA
AZOLES
BIOGEOCHEMISTRY
BITUMINOUS MATERIALS
CARBONACEOUS MATERIALS
CARBOXYLIC ACIDS
CHEMICAL ANALYSIS
CHEMISTRY
CHLOROPHYLL
ENERGY SOURCES
FOSSIL FUELS
FUELS
GEOCHEMISTRY
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MATERIALS
OIL SHALES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PETROLEUM
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
PYRROLES
QUANTITATIVE CHEMICAL ANALYSIS
ROCKS
SEDIMENTARY ROCKS
SHALES
SPECTRA