Vera M. Kolb

Bio: Vera M. Kolb is an academic researcher from University of Wisconsin–Parkside. The author has contributed to research in topics: Desert varnish & Ring (chemistry). The author has an hindex of 15, co-authored 93 publications receiving 894 citations. Previous affiliations of Vera M. Kolb include Southern Illinois University Carbondale.

Silicate complexes of sugars in aqueous solution.

Abstract: Certain sugars react readily with basic silicic acid to form soluble 2/1 (sugar/silicic acid) silicate complexes. Failure of monohydroxy compounds to give soluble products under these conditions indicates that the sugar silicates are chelates: five-membered diolato rings. Only furanose forms react. Pyranose sugars are stable under these conditions. Because all glycosides fail to react with silicic acid under these conditions, reaction appears to involve the anomeric position (C1 in aldoses, C2 in ketoses), which has a more acidic hydroxy group. Reaction is completed only when the anomeric hydroxy group is cis to an adjacent hydroxy group. The appropriate furanose form must have sufficient natural abundance and solubility to provide an observable product, as measured by 29Si and 13C NMR spectroscopy. These structural and practical constraints rationalize the successful reaction of the monosaccharides ribose, xylose, lyxose, talose, psicose, fructose, sorbose, and tagatose and the disaccharides lactulose, ...

Investigation of hormone-receptor interactions by means of fluorescence labeling.

Abstract: Fluorescent-labeled hormones can be used to study hormone-receptor interactions by means of fluorescence polarization, visualization by fluorescence microscopy, or separation methods, e.g. , dextran-coated charcoal. Subcellular fragments, single cells, and tissue preparations are amenable to study; in this work rat uterine cytosol was used unless otherwise noted. Estrone labeled with fluorescein at position 17 gives 50% inhibition in the radiometric dextran-coated charcoal assay at 8.3 × 10 -7 m as compared to 3.4 and 3.5 × 10 -8 m for diethylstilbestrol and estradiol, respectively. Scatchard plots from fluorescence polarization are hyperbolic and consistent with two classes of binding sites having association constants 5.6 × 10 10 and 6.4 × 10 7 m -1 . Binding by high-affinity sites, which were present at about 3 times the concentration of “specific” sites (radiometric dextran-coated charcoal assay), was abrogated by estradiol or diethylstilbestrol. Kinetic measurements showed that binding sites that can be blocked by excess estradiol or diethylstilbestrol are those that are both slowly associating and slowly dissociating. Staining of tissues by estrone labeled with fluorescein at position 17 as seen in the fluorescence microscope showed specificity. In normal rat uterus only epithelial cells were stained. In one human infiltrating ductal carcinoma only the malignant ductoid elements stained, while in another there was essentially no staining.

Baking black opal in the desert sun: The importance of silica in desert varnish

Abstract: Desert varnish, a widespread black manganese-rich rock coating, contains labile organic compounds, but a mechanism for its formation and for their preservation remains unproven. Using Raman spectroscopy, X-ray diffraction, and scanning transmission electron microscopy, we analyzed varnish and found amorphous hydrated silica (opal) and the silica mineral moganite, similar to findings we have reported from siliceous hot-spring deposits. We suggest that the slow dissolution of silica from anhydrous and hydrous minerals, and its subsequent gelling, condensation, and hardening, provides a simple explanation of a formation mechanism for desert varnish and silica glazes and the incorporation of organic material from local environments. These chemical signatures, sequestered in silica, provide valuable information about terrestrial and extraterrestrial paleoenvironments.

Biological and organic constiuents of desert varnish: review and new hypotheses

Abstract: Desert varnish coatings are found on rock surfaces throughout arid regions of the world. Rock varnishes may exist on Mars, as suggested by some observations on both Viking and Mars Pathfinder landing sites. There has long been a debate as to whether varnish coatings are microbially mediated or deposited by inorganic processes. Dozens of bacteria have been cultured from the surface of varnish coatings and recently the molecular ecology of varnish coatings have been characterized using 16S rRNA techniques. Colonies of micro colonial fungus are associated with varnish coatings but it is unclear whether bacteria or fungus are directly involved in varnish formation. Another alternative is the incorporation of microbial components into varnish coatings either by complexation with metals or in association with clays. For instance polysaccharides found in bacterial cell walls contain linear polymers of sugars that may be preserved in arid conditions when complexed with usual varnish components such as calcium, aluminum, silicon, iron and manganese. Understanding the organic components of desert varnish may help to resolve the question of the mechanism of formation of rock coatings, biomineralization processes and bacterial fossils and how to detect past microbially activity on planets.

Mineral induced phosphorylation of glycolate ion - a metaphor in chemical evolution

Abstract: Bilateral surface-active minerals with excess positive charge concentrate glycolate and trimetaphosphate ion from l0(-3) m aqueous solution to half-saturation of the internal surface sites, and induce phosphorylation of glycolate ion in the mineral with trimetaphosphate, sorbed from l0(-2) m solution By utilizing reactants from dilute solution at near-neutral pH, and eliminating the need for participating organic nitrogen compounds, the reaction comprises several elements considered necessary for geochemical realism in models for molecular evolution

The Theory of Island Biogeography

Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

Molecular cues to implantation

Abstract: Successful implantation is the result of reciprocal interactions between the implantation-competent blastocyst and receptive uterus. Although various cellular aspects and molecular pathways of this dialogue have been identified, a comprehensive understanding of the implantation process is still missing. The receptive state of the uterus, which lasts for a limited period, is defined as the time when the uterine environment is conducive to blastocyst acceptance and implantation. A better understanding of the molecular signals that regulate uterine receptivity and implantation competency of the blastocyst is of clinical relevance because unraveling the nature of these signals may lead to strategies to correct implantation failure and improve pregnancy rates. Gene expression studies and genetically engineered mouse models have provided valuable clues to the implantation process with respect to specific growth factors, cytokines, lipid mediators, adhesion molecules, and transcription factors. However, a staggering amount of information from microarray experiments is also being generated at a rapid pace. If properly annotated and explored, this information will expand our knowledge regarding yet-to-be-identified unique, complementary, and/or redundant molecular pathways in implantation. It is hoped that the forthcoming information will generate new ideas and concepts for a process that is essential for maintaining procreation and solving major reproductive health issues in women.