Graphene Oxide-Supported Microwell Grids for Preparing Cryo-EM Samples with Controlled Ice Thickness

Cryogenic-electron microscopy (cryo-EM) is the preferred method to determine 3D structures of proteins and to study diverse material systems that intrinsically have radiation or air sensitivity. Current cryo-EM sample preparation methods provide limited control over the sample quality, which limits the efficiency and high throughput of 3D structure analysis. This is partly because it is difficult to control the thickness of the vitreous ice that embeds specimens, in the range of nanoscale, depending on the size and type of materials of interest. Thus, there is a need for fine regulation of the thickness of vitreous ice to deliver consistent high signal-to-noise ratios for low-contrast biological specimens. Herein, an advanced silicon-chip-based device is developed which has a regular array of micropatterned holes with a graphene oxide (GO) window on freestanding silicon nitride (Si_x N_y ). Accurately regulated depths of micropatterned holes enable precise control of vitreous ice thickness. Furthermore, GO window with affinity for biomolecules can facilitate concentration of the sample molecules at a higher level. Incorporation of micropatterned chips with a GO window enhances cryo-EM imaging for various nanoscale biological samples including human immunodeficiency viral particles, groEL tetradecamers, apoferritin octahedral, aldolase homotetramer complexes, and tau filaments, as well as inorganic materials.

Association of race/ethnicity, socioeconomic status, acculturation, and environmental factors with risk of overweight among adolescents in California, 2003

INTRODUCTION

Little has been published about racial/ethnic differences in the prevalence of overweight among adolescents that accounts in detail for socioeconomic status, acculturation, and behavioral and environmental factors. Increased understanding of factors associated with overweight can provide a rational basis for developing interventions to address the obesity epidemic in the United States.

METHODS

Using a cross-sectional analysis of data from adolescents who participated in the California Health Interview Survey 2003, we estimated the prevalence of overweight and at risk of overweight, combined as a single measure (AROW, body mass index > or =85th percentile). We used logistic regression models to examine associations between AROW and risk factors.

RESULTS

Twenty-nine percent of California adolescents were AROW. The prevalence of AROW differed significantly by sex and race. Boys were more likely than girls to be AROW (33% vs 25%). American Indians/Pacific Islanders/others (39%) were at highest risk, followed by Hispanics (37%), blacks (35%), whites (23%), and Asians (15%). For boys, older age, Hispanic or American Indian/Pacific Islander/other race/ethnicity, lower education of parents, and longer residence in the United States were significantly associated with AROW. For girls, Hispanic or black race/ethnicity, lower education of parents, and poor dietary habits were significantly associated with AROW.

CONCLUSION

The high prevalence of AROW among California adolescents in most racial/ethnic groups indicates the need for culturally specific and appropriate interventions to prevent and treat overweight.

Structure-activity relationships of pyrimidine nucleosides as antiviral agents for human immunodeficiency virus type 1 in peripheral blood mononuclear cells

The structure-activity relationships of several pyrimidine nucleosides related to 3'-azido-3'-deoxythymidine (AZT) were determined in human immunodeficiency virus type 1 (HIV-1) infected human peripheral blood mononuclear cells. These studies indicated that nucleosides with a 3'-azido group on the sugar ring exhibited the most potent antiviral activity. Substitution at C-5 with H, CH3, and C2H5 produced derivatives with the highest potency, whereas alkyl functions greater than C2, including bromovinyl substitution reduced the antiviral potency significantly. Changing the 3'-azido function to an amino or iodo group reduced the antiviral activity. Replacement of the uracil ring by cytosine or 5-methylcytosine produced analogues with high potency and low toxicity. Modification of the 5'-hydroxy group markedly reduced the antiviral activity. Similarly, various C-nucleoside analogues related to AZT and 2',3'-dideoxycytidine were inactive and nontoxic. From these systematic studies 3'-azido-2',3'-dideoxyuridine (5a), 3'-azido-5-ethyl-2',3'-dideoxyuridine (5c), and 3'-azido-2',3'-dideoxycytidine (7a) and its 5-methyl analogue (7b) were identified as potent and selective anti-HIV-1 agent in primary human lymphocytes.