Hybrid Oleate-Iodide Ligand Shell for Air-Stable PbSe Nanocrystals and Superstructures.

A postsynthetic treatment is presented to improve the air stability of PbSe nanocrystals (NCs) and PbSe square superstructures. The addition of z-type Pb(oleate)2 ligands together with x-type iodide ligands creates a hybrid ligand shell containing both ligands. The air stability of the PbSe NCs is checked by enduring absorption spectroscopy under ambient conditions. With a combined NaI + Pb(oleate)2 treatment, the absorption spectrum remains unchanged for several days under ambient conditions. Fourier transform infrared spectroscopy shows that the surface coordination of the oleate ligands changes by the chemical treatment: from mixed chelating bidentate + bridging to Pb for the pristine nanocrystals to almost exclusive chelating bidentate coordination after chemical passivation. The shift of the C-H stretching vibration shows that the oleate hydrocarbon layer is in a more liquidlike state after the chemical treatment, suggesting that oleate and iodide ligands are often present on adjacent surface positions.

Reactor for nano-focused x-ray diffraction and imaging under catalytic in situ conditions.

A reactor cell for in situ studies of individual catalyst nanoparticles or surfaces by nano-focused (coherent) x-ray diffraction has been developed. Catalytic reactions can be studied in flow mode in a pressure range of 10-2-103 mbar and temperatures up to 900 °C. This instrument bridges the pressure and materials gap at the same time within one experimental setup. It allows us to probe in situ the structure (e.g., shape, size, strain, faceting, composition, and defects) of individual nanoparticles using a nano-focused x-ray beam. Here, the setup was used to observe strain and facet evolution of individual model Pt catalysts during in situ experiments. It can be used for heating other (non-catalytically active) nanoparticles (e.g., nanowires) in inert or reactive gas atmospheres or vacuum as well.

Disease-specific alterations in frontal cortex brain proteins in schizophrenia, bipolar disorder, and major depressive disorder. The Stanley Neuropathology Consortium.

Severe psychiatric disorders such as schizophrenia, bipolar disorder and major depressive disorder are brain diseases of unknown origin. No biological marker has been documented at the pathological, cellular, or molecular level, suggesting that a number of complex but subtle changes underlie these illnesses. We have used proteomic technology to survey postmortem tissue to identify changes linked to the various diseases. Proteomics uses two-dimensional gel electrophoresis and mass spectrometric sequencing of proteins to allow the comparison of subsets of expressed proteins among a large number of samples. This form of analysis was combined with a multivariate statistical model to study changes in protein levels in 89 frontal cortices obtained postmortem from individuals with schizophrenia, bipolar disorder, major depressive disorder, and non-psychiatric controls. We identified eight protein species that display disease-specific alterations in level in the frontal cortex. Six show decreases compared with the non-psychiatric controls for one or more diseases. Four of these are forms of glial fibrillary acidic protein (GFAP), one is dihydropyrimidinase-related protein 2, and the sixth is ubiquinone cytochrome c reductase core protein 1. Two spots, carbonic anhydrase 1 and fructose biphosphate aldolase C, show increase in one or more diseases compared to controls. Proteomic analysis may identify novel pathogenic mechanisms of human neuropsychiatric diseases.

Analysis of a randomly assorted cDNA library from BW 5147 lymphoid cells. Frequency estimates based on computer aided concatenation matching of 2D gel polypeptide products.

A cDNA library was divided into 291 sectors of low complexity, 800-1000 recombinant phage plaques per sector. Aliquots of DNA from sectors prepared from high titer phage were subjected to in vitro transcription using T7 polymerase and thereafter RNA was translated in a cell-free rabbit reticulocyte system in the presence of [35S] methionine. The resulting polypeptides were separated by 2D gel electrophoresis. Radiofluorographs of the gels prepared from 10 sectors were subjected to scanning and image analysis. A multilevel spot matching procedure was employed allowing us to recognise spot occurrence in the 10 sectors. The number of detected polypeptide spots per sector varied between 147 and 325. Overall, 1082 different spots were counted totalling 1983 spots considering multiple entries. The distribution of the spots and the frequency distribution of the RNA population among the 10 sectors are shown. The highest detected frequency is 10(-2), while one half of the RNA molecular species are present at a frequency of 10(-3) or lower.

Simultaneous measurement of hundreds of liver proteins: application in assessment of liver function.

Proteins implement most biological functions at the molecular level. As one might expect based on this fact, it appears that the altered functional states associated with toxic effects involve changes in the abundance or structure of proteins. Although numerous specific assays exist to measure changes in the abundance of individual proteins, practical limitations have prevented widespread use of multiple protein assays for the global characterization of toxicity. Recent developments in protein analytical technology are rapidly changing this picture. Two-dimensional gel electrophoresis, a technique capable of resolving and quantitating hundreds of proteins simultaneously, is becoming an automated, high-throughput tool. In parallel, techniques have been developed that allow the resulting deluge of protein measurements to be organized into a prototype Molecular Effects Database describing xenobiotic effects in rodent liver. This database can detect, classify, and characterize a broad range of liver toxicity mechanisms. It currently contains approximately 10 million protein measurements, including data on the liver effects of 43 compounds, with a further 50 compounds to be added in 1995. Observed effects range from very broad (sex steroids alter levels of 45% of all liver proteins) to very specific (e.g., hepatic hydroxymethyl glutaryl coenzyme A reductase inhibitors). Companion 2-dimensional databases describing rodent brain and kidney have been initiated, as have linkages to the genomic sequence databases. Assimilation of this approach into research and regulatory toxicology poses an interesting challenge--one that is likely to lead to a radically more sophisticated understanding of toxicity and its biological basis.

An updated two-dimensional gel database of rat liver proteins useful in gene regulation and drug effect studies.

We have improved upon the reference two-dimensional (2-D) electrophoretic map of rat liver proteins originally published in 1991 (N. L. Anderson et al., Electrophoresis 1991, 12, 907-930). A total of 53 proteins (102 spots) are now identified, many by microsequencing. In most cases, spots cut from wet, Coomassie Blue stained 2-D gels were submitted to internal tryptic digestion [2], and individual peptides, separated by high-performance liquid chromatography (HPLC), were sequenced using a Perkin-Elmer 477A sequenator. Additional spots were identified using specific antibodies.

A two-dimensional gel database of rat liver proteins useful in gene regulation and drug effects studies.

A standard two-dimensional (2-D) protein map of Fischer 344 rat liver (F344MST3) is presented, with a tabular listing of more than 1200 protein species. Sodium dodecyl sulfate (SDS) molecular mass and isoelectric point have been established, based on positions of numerous internal standards. This map has been used to connect and compare hundreds of 2-D gels of rat liver samples from a variety of studies, and forms the nucleus of an expanding database describing rat liver proteins and their regulation by various drugs and toxic agents. An example of such a study, involving regulation of cholesterol synthesis by cholesterol-lowering drugs and a high-cholesterol diet, is presented. Since the map has been obtained with a widely used and highly reproducible 2-D gel system (the Iso-Dalt system), it can be directly related to an expanding body of work in other laboratories.

Protein changes occurring during storage of platelet concentrates. A two-dimensional gel electrophoretic analysis.

The changes in thrombocyte proteins during 22 degrees C storage of platelet concentrates (PC) were studied. To prepare a reference protein "map" of stored PC, platelet samples were taken on days 1, 7, and 21. The platelet proteins were separated by isoelectric focusing (first-dimension) followed by second-dimension polyacrylamide gradient gel electrophoresis with sodium dodecylsulfate (2D). The silver-stained gels were analyzed by computer to obtain a composite map of stored PC proteins. The pattern seen on day 1 changed during 7 days of storage, with 30 proteins increasing or decreasing in spot density. In general, the spot density for lower-molecular-weight proteins increased, whereas that for higher-molecular-weight proteins decreased. Membrane proteins of intact fresh and stored platelets were labeled with 3H using sodium metaperiodate-[3H]NaBH4 and with 125I using lactoperoxidase-H2O2. A comparison on the fluorographs of 2D gels of [3H]NaBH4-labeled platelet proteins showed several protein spots in the stored Day 7 sample that had not been seen in the Day 1 sample. Similarly, for the autoradiographs, several 125I-labeled proteins detected in Day 7 PC were not seen in the Day 1 samples. The results provide evidence that platelet proteins are altered during PC storage and that these changes involve platelet membrane proteins.

Two-dimensional gel electrophoresis of proteins for genetic studies in Douglas fir (Pseudotsuga menziesii).

A method of two-dimensional gel electrophoresis of proteins from Douglas fir needles is described. Extraction in the presence of sodium dodecyl sulfate (SDS) and 2-mercaptoethanol followed by heating at 100 degrees C produces reliable two-dimensional gels which are convenient for genetic studies. Three genotypes from different geographical origins have been compared: among 225 loci expressed, 22 display regulatory variations and 7 show allelic variations. Thus it is now possible to undertake the genetic study of Douglas fir using this powerful technique.

Global approaches to quantitative analysis of gene-expression patterns observed by use of two-dimensional gel electrophoresis.

A major difficulty in the use of two-dimensional protein maps to identify and classify cell types is the problem of acquiring, selecting, and analyzing quantitative data on hundreds of protein spots. Here we use methods of multivariate statistics to analyze the differences among a panel of human cell lines, in some cases involving quantitative data on more than 250 proteins. Principal-component and cluster-analysis techniques show that the lines can be easily distinguished, even by using the subset of proteins present in all cells. A preliminary analysis of the protein changes brought about by phorbol ester-induced differentiation of the line U937 is included.

Study on nuclear and cytoplasmic genome expression in wheat by two-dimensional gel electrophoresis : 2. Genetic differences between two lines and two groups of cytoplasms at five developmental stages or organs.

Two-dimensional gel electrophoresis of denaturated proteins were performed at five developmental stages or organs (hereafter referred to as stage-organs) on two wheat lines with four different cytoplasms. Five hundred and fifty to 712 reproducible spots were scored depending on the stage-organ. Each stage-organ is unambiguously characterized and several types of control of protein quantity are recorded. Post-translational modifications are hypothetized and may sometimes be stagespecific. Two cytoplasmic patterns are found: one for the euplasmic lines with Triticum aestivum cytoplasm and one for the alloplasmic lines with Aegilops juvenalis, Ae. ventricosa and Ae. kotschyi cytoplasms. Cytoplasmic variation is observed for 28 spots showing position difference, all of which are probably products of the LS gene, and for four spots showing differences for regulation of protein quantity. Nuclear variation between 'Chinese Spring' and 'Selkirk' is found for 20 allelic differences and for 20 regulatory systems, the latter number being probably underestimated.

Study on nuclear and cytoplasmic genome expression in wheat by two-dimensional gel electrophoresis : 1. First results on 18 alloplasmic lines.

In this first analysis the protein patterns obtained by two-dimensional gel electrophoresis of 8 day-old leaves from 18 alloplasmic wheat lines are compared. From 440 spots retained on the basis of their reproducibility, 36 proteins were observed to vary in different cytoplasms, allowing us to distinguish the T. aestivum cytoplasm from 5 Aegilops cytoplasms. Twenty-four of the 36 variable proteins could be structurally related to the large subunit of RuBPCase. Nuclear variation between 3 wheat varieties was observed for 14 proteins.