The DNA binding domain of the Vibrio vulnificus SmcR transcription factor is flexible and binds diverse DNA sequences.

Quorum sensing gene expression in vibrios is regulated by the LuxR/HapR family of transcriptional factors, which includes Vibrio vulnificus SmcR. The consensus binding site of Vibrio LuxR/HapR/SmcR proteins is palindromic but highly degenerate with sequence variations at each promoter. To examine the mechanism by which SmcR recognizes diverse DNA sites, we generated SmcR separation-of-function mutants that either repress or activate transcription but not both. SmcR N55I is restricted in recognition of single base-pair variations in DNA binding site sequences and thus is defective at transcription activation but retains interaction with RNA polymerase (RNAP) alpha. SmcR S76A, L139R and N142D substitutions disrupt the interaction with RNAP alpha but retain functional DNA binding activity. X-ray crystallography and small angle X-ray scattering data show that the SmcR DNA binding domain exists in two conformations (wide and narrow), and the protein complex forms a mixture of dimers and tetramers in solution. The three RNAP interaction-deficient variants also have two DNA binding domain conformations, whereas SmcR N55I exhibits only the wide conformation. These data support a model in which two mechanisms drive SmcR transcriptional activation: interaction with RNAP and a multi-conformational DNA binding domain that permits recognition of variable DNA sites.

Complexity of Uranyl Peroxide Cluster Speciation from Alkali-Directed Oxidative Dissolution of Uranium Dioxide.

Solid UO2 dissolution and uranium speciation in aqueous solutions that promote formation of uranyl peroxide macroanions was examined, with a focus on the role of alkali metals. UO2 powders were dissolved in solutions containing XOH (X = Li, Na, K) and 30% H2O2. Inductively coupled plasma optical emission spectrometry (ICP-OES) measurements of solutions revealed linear trends of uranium versus alkali concentration in solutions resulting from oxidative dissolution of UO2, with X:U molar ratios of 1.0, showing that alkali availability determines the U concentrations in solution. The maximum U concentration in solution was 4.20 × 105 parts per million (ppm), which is comparable to concentrations attained by dissolving UO2 in boiling nitric acid, and was achieved by lithium hydroxide promoted dissolution. Raman spectroscopy and electrospray ionization mass spectrometry (ESI-MS) of solutions indicate that dissolution is accompanied by the formation of various uranyl peroxide cluster species, the identity of which is alkali concentration dependent, revealing remarkably complex speciation at high concentrations of base.

A Novel Multifactorial Approach to Developing Mild Laundry Detergents and Assessing Their Relative Mildness

INTRODUCTION: Dermatologists are becoming more aware of the irritant and allergic potential of laundry detergents that incorporate harsh surfactants and potentially sensitizing ingredients. It is difficult however for the physician to distinguish one laundry detergent from another because the only distinguishing feature advertised tends to be the lack of dyes and fragrances. DESIGN: A new objective method was developed for measuring the harshness of laundry detergents using a three-pronged laboratory testing approach consisting of zein, corneosurfametry, and cytokine testing. Combing these methods, a Detergent Mildness Index was created which conveniently provides a single value by which products can be compared. RESULTS: A new mild laundry detergent was formulated with ingredients carefully selected by dermatologists who are experts in con-tact dermatitis. The irritancy potential of the formula was measured using the Detergent mildness index score. Compared to 11 other commercial laundry detergents marketed for sensitive skin, the new formula is measurably the mildest formula. DISCUSSION: The Detergent Mildness Index provides dermatologists with an objective method to compare commercial laundry deter-gents. Currently the only method available is patch testing, this new test is able to more finely differentiate between products and thus enables more informed recommendations on laundry detergent choices for their patients with sensitive skin.

Assessing the relationship between vitamin D3 and stratum corneum hydration for the treatment of xerotic skin.

Vitamin D(3) has been called the "sunshine" vitamin since the formation of vitamin D is mediated by exposure to sunlight. Vitamin D(3) is linked to many health benefits, however serum levels of vitamin D(3) have been decreasing over the last few decades and the lower levels of vitamin D(3) may have consequences on normal physiology. We investigated the association between serum 25-hydroxyvitamin D (25(OH)D) levels and stratum corneum conductance as well as the effect of topical application of cholecalciferol (vitamin D(3)) on dry skin. Eighty three subjects were recruited and blood serum levels and skin conductance measurements were taken after a one week washout. A correlation was observed between vitamin D levels and skin moisture content, individuals with lower levels of vitamin D had lower average skin moisture. Subsequently, a 3-week split leg, randomized, vehicle controlled clinical study was conducted on a subset of 61 of the above individuals who were identified with non-sufficient vitamin D serum levels. Topical supplementation with cholecalciferol significantly increased measurements of skin moisturization and resulted in improvements in subjective clinical grading of dry skin. Taken together our finding suggest a relationship between serum vitamin D(3) (25(OH)D) levels and hydration of the stratum corneum and further demonstrate the skin moisture benefit from topical application of vitamin D(3).