Chemical analysis of acoustically levitated drops by Raman spectroscopy

An experimental apparatus combining Raman spectroscopy with acoustic levitation, Raman acoustic levitation spectroscopy (RALS), is investigated in the field of physical and chemical analytics. Whereas acoustic levitation enables the contactless handling of microsized samples, Raman spectroscopy offers the advantage of a noninvasive method without complex sample preparation. After carrying out some systematic tests to probe the sensitivity of the technique to drop size, shape, and position, RALS has been successfully applied in monitoring sample dilution and preconcentration, evaporation, crystallization, an acid–base reaction, and analytes in a surface-enhanced Raman spectroscopy colloidal suspension

Sample Handling and Chemical Kinetics in an Acoustically Levitated Drop Microreactor

Accurate measurement of enzyme kinetics is an essential part of understanding the mechanisms of biochemical reactions. The typical means of studying such systems use stirred cuvettes, stopped-flow apparatus, microfluidic systems, or other small sample containers. These methods may prove to be problematic if reactants or products adsorb to or react with the container’s surface. As an alternative approach, we have developed an acoustically-levitated drop reactor eventually intended to study enzyme-catalyzed reaction kinetics related to free radical and oxidative stress chemistry. Microliter-scale droplet generation, reactant introduction, maintenance, and fluid removal are all important aspects in conducting reactions in a levitated drop. A three capillary bundle system has been developed to address these needs. We report kinetic measurements for both luminol chemiluminescence and the reaction of pyruvate with nicotinamide adenine dinucleotide, catalyzed by lactate dehydrogenase, to demonstrate the feasibility of using a levitated drop in conjunction with the developed capillary sample handling system as a microreactor

Racoleus, a new genus of sterile filamentous lichen-forming fungi from the tropics, with observations on the nomenclature and typification of Cystocoleus and Racodium

Racoleus trichophorus gen. sp. nov. is described for a tropical sterile filamentous lichenized fungus which overgrows various crustose lichens on bark. It shares some features with Cystocoleus and Racodium, but is unique in having non-lichenized long lateral spines. The genus, which is known from China, the Ivory Coast, and Peru, is of uncertain systematic position; on the basis of morphological similarities, however, it may be referred to “? Capnodiales (incertae sedis)” ad interim. In addition, the nomenclature and typification of the monotypic genera Cystocoleus and Racodium are reviewed, and lectotypes selected for the type of each. The available information on the ecology and distribution of these two genera is also summarized, and scanning electron micrographs (SEM) of all three species are presented for the first time