Chlorophyll Derivatives in Middle Eocene Sediments

Chemistry of porphyrins in fossil plants and animals

Porphyrins are macrocyclic tetrapyrrole derivatives that are widely distributed in nature. They are often complexed with a metal ion located in the center of the ring system and may be modified by various substituents including additional rings, or by ring opening, which leads to a plethora of different functions. Due to their extended conjugated aromatic ring system, porphyrins absorb light in the visible range and therefore show characteristic colors. Well-known natural porphyrins include the red-colored heme present in hemoglobin, which is responsible for blood oxygen transport, and the chlorophylls in some bacteria and in plants which are utilized for photosynthesis. Porphyrins are mostly lipophilic pigments that display relatively high chemical stability. Therefore, they can even survive hundreds of millions of years. The present review article provides an overview of natural porphyrins, their chemical structures, and properties. A special focus is put on porphyrins discovered in the fossil record. Examples will be highlighted, and information on their chemical analysis will be provided. We anticipate that the development of novel analytical methods with increased sensitivity will prompt new discoveries of porphyrins in fossils.

Selective and mild fractionation of microalgal proteins and pigments using aqueous two-phase systems

BACKGROUND

Microalgal biomass is generally used to produce a single product instead of valorizing all of the cellular components. The biomass production and downstream processes are too expensive if only one product is valorized. A new approach was proposed for the simultaneous and selective partitioning of pigments and proteins from disrupted Neochloris oleoabundans cultivated under saline and freshwater conditions.

RESULTS

An aqueous two-phase system composed of polyethylene glycol and cholinium dihydrogen phosphate selectively separated microalgal pigments from microalgal proteins. 97.3 ± 1.0% of lutein and 51.6 ± 2.3% of chlorophyll were recovered in the polymer-rich phase. Simultaneously, up to 92.2 ± 2.0% of proteins were recovered in a third phase (interface) in between the aqueous phases (interface). The recovered proteins, including Rubisco with a molecular weight of ∼560 kDa, seem to be intact and pigments did not suffer degradation, demonstrating the mildness of this system for fractionating microalgal biomolecules.

CONCLUSION

The ability of aqueous two-phase systems (ATPSs) to simultaneously and efficiently fractionate different biomolecules in a mild manner from disrupted microalgae is demonstrated. This is an important step towards the development of a multiproduct microalgae biorefinery. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Ultrastructure and cytochemistry of Miocene angiosperm leaf tissues

Angiosperm leaf fossils (16.7-25 x 10(6) years by potassium/argon dating) referable to Zelkova were isolated from pyroclastic deposits in the Succor Creek Formation, Oregon. These fossils reveal a three-dimensional structure in mesophyll cell layers and vascular bundles, while transmission electron microscopy of fixed tissues reveals well-preserved chloroplasts with grana stacks and starch, as well as nuclei with condensed chromatin. Transmission electron microscopy indicates that cell walls retain a cellulosic microfibrillar architecture, while ultrastructural and cytochemical confirmation is presented for chloroplast starch and the presence of native cellulose. The preservation of cell walls and cytologic structures in fossil materials of this age indicates an unusually mild fossilization process attending the post-depositional maturation of associated sediments. The preservation observed appears to be associated with rapid physical dehydration coupled with endogenous fixation by organic acids (possibly tannins and/or chlorophyll derivatives).

Sunlight-induced cancer: some new aspects and implications of the xeroderma pigmentosum model

Symptoms of xeroderma pigmentosum, a hereditary disease characterized by accelerated light-induced ageing of the skin, are due to deficiencies in the repair of damaged DNA. Following UV irradiation a high incidence of thioguanine-resistant mutations have been observed, which may be a model for the abnormally high incidence of freckling and benign and malignant transformation observed in these patients. Cells from patients with Cockayne's syndrome and trichothiodystrophy have also been shown to be hypermutable by UV radiation with a similar DNA repair defect, but unlike xeroderma pigmentosum patients they do not experience a higher incidence of skin cancer or freckling. An immunological defect may be a further crucial factor determining the dermatological symptoms of xeroderma pigmentosum patients. Much can be learned about the way normal individuals function from a study of aberrant functioning of individuals with defined genetic deficiencies. In the field of senescence of the skin, the disease xeroderma pigmentosum (XP) has been of particular value, as the exposed skin of these sun-sensitive individuals shows at an early age many of the features of aged sun-exposed skin of normal individuals. These features of XP skin include hyperkeratosis, freckling, benign lesions and malignant tumours, including melanomas. A full discussion of this syndrome has been given by Kraemer et al.

THE DISTRIBUTION OF LIGNIN DERIVATIVES IN FOSSIL PLANTS

Lignin derivatives have been obtained from a range of sub-fossil woods and fossil plant compressions by cupric oxide oxidation. Fossil woods yield essentially the same products as wood from living spermatophytes. Although some demethoxylation of the phenolic aldehydes occurs during fossilization, the overall difference between conifer and angiosperm wood is maintained. Compressions of varied plant organs yield recognizable phenolic aldehydes, though often in small amounts.

Evidence of Paleozoic Chromosomes from Lycopod Microgametophytes

A Pennsylvanian arborescent lycopod cone, Lepidostrobus schopfii, has microspores that have been found to have intracellular features that are interpreted as nuclei and mitotic chromosomes. The cellularized gametophytes conform to the early stages of growth that occur in modern Selaginella microgametophytes. Since the megagametophyte of L. schopfii is similar in development to extant species of Isoetes, the fossil now is known to have portions of its life cycle in common with both Selaginella and Isoetes.

Flavonoid and Other Chemical Constituents of Fossil Miocene Celtis and Ulmus (Succor Creek Flora)

Organic solvent extractions of green-colored fossil Celtis sp. and Ulmus sp. leaves (36 to 25 x 10(6) years old) indicate the preservation of quercetin-3-O-glycosides, apigenin and luteolin carbon glycosides, methyl pheophorbide a, and a consortium of other organic constituents. Comparisons between referable fossil and extant taxa indicate a high level of phytochemical fidelity. The preservation of O-glycosides indicates a mild postdepositional environment during fossilization.

Flavonoids and Other Chemical Constituents of Fossil Miocene Zelkova (Ulmaceae)

Organic solvent extractions of Zelkova oregoniana, a Miocene angiosperm compression fossil, indicate the chemical preservation of kaempferol, dihydrokaempferol, an n-alkane chain length range of 10 to 32 carbons, hydroxy acids, steranes, triterpenoids, and methyl pheophorbide a. This appears to be the oldest occurrence of flavonoids in fossil sediments reported.