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The standard reference libraries and associated custom software provided by the National Institute of Standards and Technology's Mass Spectrometry Data Center (NIST MSDC) are described with a focus on assisting the seized drug analyst with the identification of fentanyl‐related substances (FRS). These tools are particularly useful when encountering novel substances when no certified sample is available. The MSDC provides three standard reference mass spectral libraries, as well as six software packages for mass spectral analysis, reference library searching, data interpretation, and measurement uncertainty estimation. Each of these libraries and software packages are described with references to the original publications provided. Examples of fentanyl identification by gas chromatography–mass spectrometry (GC–MS) and by direct analysis in real‐time (DART) mass spectrometry are given. A link to online tutorials is provided. [ABSTRACT FROM AUTHOR]

It is frequently recounted that shortly before Michelangelo died, the eighty-eight-year-old artist sat before a fire and burned many drawings. Critical examination reveals various motivations for such a destructive act and elicits suggestions for what Michelangelo might have burned. Mainly because of old age and significant changes in his artistic practice, Michelangelo made far fewer drawings in his final two decades than earlier in his career. Therefore, he may have destroyed less than is usually imagined and nothing that would have impaired the completion of his current projects, most important of which was New Saint Peter's. [ABSTRACT FROM AUTHOR]

Presents information on a study which evaluated the structural properties of low-dielectric-constant porous silica thin films using a high-resolution specular x-ray reflectivity and small-angle neutron scattering. High-energy ion scattering measurements; Experimental procedure; Results and discussion; Conclusions.

Relates the history of a Michelangelo project for a reliquary tabernacle in the church of San Silvestro in Capite, Rome, Italy. Explanation of the social dynamics contained in the history; Interplay of personal, political and professional relations involved in the minor undertaking of a major artist; Removal of the boundaries of patronage, favor and friendship.

Examines the sculpture titled the `Risen Christ' by artist Michelangelo, by restoring it to its original context and discussion of its unusual and moving iconography. Description of the sculpture; Where the sculpture is located; Why the sculpture is the least known work by the artist; History of the sculpture.

A mass spectral library search algorithm that identifies compounds that differ from library compounds by a single "inert" structural component is described. This algorithm, the Hybrid Similarity Search, generates a similarity score based on matching both fragment ions and neutral losses. It employs the parameter DeltaMass, defined as the mass difference between query and library compounds, to shift neutral loss peaks in the library spectrum to match corresponding neutral loss peaks in the query spectrum. When the spectra being compared differ by a single structural feature, these matching neutral loss peaks should contain that structural feature. This method extends the scope of the library to include spectra of "nearest-neighbor" compounds that differ from library compounds by a single chemical moiety. Additionally, determination of the structural origin of the shifted peaks can aid in the determination of the chemical structure and fragmentation mechanism of the query compound. A variety of examples are presented, including the identification of designer drugs and chemical derivatives not present in the library. [ABSTRACT FROM AUTHOR]

This essay is a preliminary sketch for a book that examines Michelangelo Buonarroti's final eighteen years, from his appointment as architect of St. Peter's until his death in 1564, that is, from age seventy-one to a few weeks shy of eighty-nine. This period represents nearly a quarter of his approximately seventy-five-year artistic career, yet it remains the least familiar segment of Michelangelo's long life. It is paradoxical that in the final phase of his career, Michelangelo remained prodigiously creative and influential without being prolific--as he had been earlier in his career. His late life was concerned less with making things than with finding the courage and devotion to continue tasks that he knew he would never see to fruition, and this despite the loss of his closest friends, greatest patron, and his entire family. [ABSTRACT FROM AUTHOR]

Abstract: Recently it has been shown that the cobaltocenium cation, prepared by the laser ablation of a CoCp(CO)2/fullerene matrix, may react with alkanes and polyethylenes in the gas phase via a dehydrogenation reaction to produce [Co(Cp)2(alkadiene)]+ ions without chain scission (W.E. Wallace, Chem. Commun. 2007, 4525–4527). To better understand these experimental observations, density functional calculations were used to obtain the gas phase binding energies and molecular structures of cobaltocenium, Co(Cp)2 +, with 1,3-butadiene, 2,4-hexadiene, and 2,3-hexadiene. Calculations were conducted for both cis and trans molecular configurations, in both singlet and triplet electronic states, and with a variety of cyclopentadienyl hapticities. For 1,3-butadiene the 18-electron rule would predict a [Co(η3-Cp)2(η4-1,3-butadiene)]+, however, the lowest energy structure, [Co(η5-Cp)2(1,3-butadiene)]+, has a higher than expected cyclopentadienyl hapticity. In this structure a distance of nearly 0.5nm between the metal core and the butadiene ligand leads to very little electron sharing. Thus the detected ions are better described as non-covalent ion–molecule complexes. In turn, the lack of orbital overlap leads to a low enthalpy giving the cis-butadiene complex a −13.0kJ/mol binding energy and the trans-butadiene binding a −3.8kJ/mol binding energy. These low binding energies lead to low levels of charged alkanes in the reactive ion formation process in agreement with experimental observations. [Copyright &y& Elsevier]

Abstract: The new generation of mass spectrometers produces an astonishing amount of high-quality data in a brief period of time, leading to inevitable data analysis bottlenecks. Automated data analysis algorithms are required for rapid and repeatable processing of mass spectra containing hundreds of peaks, the part of the spectra containing information. New data processing algorithms must work with minimal user input, both to save operator time and to eliminate inevitable operator bias. Toward this end an accurate mathematical algorithm is presented that automatically locates and calculates the area beneath peaks. The promising numerical performance of this algorithm applied to raw data is presented. [Copyright &y& Elsevier]

Respirable quartz and kaolin particles were treated with fluorescent-labeled phospholipids to model contact of fibrogenic and nonfibrogenic particles with pulmonary surfactant in the alveolar regions of the lung. Particles were used to challenge rat pulmonary macrophages in vitro at times from 1 d to 10 d. The objective was to develop a quantitative method to track surfactant components that adsorb to respirable particles in the lung or inside cells. Confocal laser scanning microscopy was used to image and quantify surfactant remaining on particles internalized by cells. Results indicate that the fluorescent label is removed from quartz particles quickly, with the fluorescence intensity less than 15% of initial value at 3 d, and about 5% at 10 d. In contrast, the kaolin particle-associated fluorescence was still ~39% of initial intensity at 3 d, and 10–15% at 10 d. Unchallenged cells showed a background of ~5%, and noninternalized particles did not exhibit any loss of fluorescence over the 10-d exposure. The results indicate the method may be useful in label-removal rate studies of respirable particles in vitro, with some cautions and limitations. Results are discussed and compared with similar studies using nonimaging techniques. [ABSTRACT FROM AUTHOR]

A mathematical algorithm is presented that locates and calculates the area beneath peaks from real data using only reproducible mathematical operations and no user-selected parameters. It makes no assumptions about peak shape and requires no smoothing or preprocessing of the data. In fact, it is shown that for matrix-assisted laser desorption time-of-flight mass spectra noise exists at all frequency ranges making the smoothing of data without distortion of peak areas impossible. The algorithm is based on a time-series segmentation routine that reduces the data set to groups of three strategic points where each group defines the beginning, center, and ending of each peak located. The peak areas are found from the strategic points using a commonplace polygonal area calculation routine. Peaks with statistically insignificant height or area are then discarded. The performance of the algorithm is demonstrated on a polystyrene mass spectrum with varying degrees of noise added either mathematically or experimentally. An on-line implementation of the method, termed MassSpectator, for public use can be found at www.nist.gov/maldi. [ABSTRACT FROM AUTHOR]

We report on the surface modification of Sylgard-184 poly(dimethyl siloxane) (PDMS) networks by ultraviolet (UV) radiation and ultraviolet/ozone (UVO) treatment. The effects of the UV light wavelength and ambient conditions on the surface properties of Sylgard-184 are probed using a battery of experimental probes, including static contact angle measurements, Fourier transform infrared spectroscopy, near-edge X-ray absorption fine structure, and X-ray reflectivity. Our results reveal that when exposed to UV, the PDMS macromolecules in the surface region of Sylgard-184 undergo chain scission, involving both the main chain backbone and the side groups. The radicals formed during this process recombine and form a network whose wetting properties are similar to those of a UV-modified model PDMS. In contrast to the UV radiation, the UVO treatment causes very significant changes in the surface and near-surface structure of Sylgard-184. Specifically, the molecular oxygen and ozone created during the UVO process interact with the UV-modified specimen. As a result of these interactions, the surface of the sample contains a large number of hydrophilic (mainly –OH) groups. In addition, the material density within the first ≈5 nm reaches about 50% of that of pure silica. A major conclusion that can be drawn from the results and analysis described in this work is that the presence of the silica fillers in Sylgard-184 does not alter the surface properties of the UVO- and UV-modified Sylgard-184. [Copyright &y& Elsevier]

Investigates the development of substrate-assisted Laser Desorption/Ionization (LDI) mass spectrometric method for polyethylene analysis. Use of sample substrate and silver nitrate for cationization; Detection of oligometer using UVLDI; Application of heating model for effectiveness of using coarse metal powders.

Explains the reasons for the refusal of Michelangelo to release the painting 'Leda' to the courtier Il Pisanello sent by Alfonso d'Este to retrieve it. Pictures included in Alfonso d'Este's camerino; Reasons for Michelangelo's acceptance of the commission; Michelangelo's assistants employed by the City of Florence, Italy to aid the defense effort.

Presents a micro-historical view of the life of artist Michelangelo Buonarroti. Michelangelo's difficulties with paying large tariffs on his art works; Supervision during the loading and unloading of his art works; Ownership of a horse as a luxury during the Renaissance; Horse as an artistic recompense; Michelangelo's preoccupation with the horse.

Recent reports have demonstrated that genetically variant peptides derived from human hair shaft proteins can be used to differentiate individuals of different biogeographic origins. We report a method involving direct extraction of hair shaft proteins more sensitive than previously published methods regarding GVP detection. It involves one step for protein extraction and was found to provide reproducible results. A detailed proteomic analysis of this data is presented that led to the following four results: (i) A peptide spectral library was created and made available for download. It contains all identified peptides from this work, including GVPs that, when appropriately expanded with diverse hair‐derived peptides, can provide a routine, reliable, and sensitive means of analyzing hair digests; (ii) an analysis of artifact peptides arising from side reactions is also made using a new method for finding unexpected modifications; (iii) detailed analysis of the gel‐based method employed clearly shows the high degree of cross‐linking or protein association involved in hair digestion, with major GVPs eluting over a wide range of high molecular weights while others apparently arise from distinct non‐cross‐linked proteins; and (v) finally, we show that some of the specific GVP identifications depend on the sample preparation method. [ABSTRACT FROM AUTHOR]

MassSpectator is a novel suite of numerical algorithms that accurately locates and calculates the area beneath peaks from real mass spectral data by using only reproducible mathematical operations. It requires no user-selected parameters but does require a background spectrum to determine instrumental noise. Such a fully automated algorithm is useful for rapid and repeatable processing of mass spectral data containing hundreds of peaks. MassSpectator represents a first attempt to create an unbiased method using time series segmentation to analyze mass spectral data.

Fentanyl analogs are a class of designer drugs that are particularly challenging to unambiguously identify due to the mass spectral and retention time similarities of unique compounds. In this paper, we use agglomerative hierarchical clustering to explore the measurement diversity of fentanyl analogs and better understand the challenge of unambiguous identifications using analytical techniques traditionally available to drug chemists. We consider four measurements in particular: gas chromatography retention indices, electron ionization mass spectra, electrospray ionization tandem mass spectra, and direct analysis in real time mass spectra. Our analysis demonstrates how simultaneously considering data from multiple measurement techniques increases the observable measurement diversity of fentanyl analogs, which can reduce identification ambiguity. This paper further supports the use of multiple analytical techniques to identify fentanyl analogs (among other substances), as is recommended by the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG). [ABSTRACT FROM AUTHOR]

Rationale The metabolite profiling of a NIST plasma Standard Reference Material (SRM 1950) on different liquid chromatography/mass spectrometry (LC/MS) platforms showed significant differences. Although these findings suggest caution when interpreting metabolomics results, the degree of overlap of both profiles allowed us to use tandem mass spectral libraries of recurrent spectra to evaluate to what extent these results are transferable across platforms and to develop cross-platform chemical signatures. Methods Non-targeted global metabolite profiles of SRM 1950 were obtained on different LC/MS platforms using reversed-phase chromatography and different chromatographic scales (conventional HPLC, UHPLC and nanoLC). The data processing and the metabolite differential analysis were carried out using publically available (XCMS), proprietary (Mass Profiler Professional) and in-house software (NIST pipeline). Results Repeatability and intermediate precision showed that the non-targeted SRM 1950 profiling was highly reproducible when working on the same platform (relative standard deviation (RSD) <2%); however, substantial differences were found in the LC/MS patterns originating on different platforms or even using different chromatographic scales (conventional HPLC, UHPLC and nanoLC) on the same platform. A substantial degree of overlap (common molecular features) was also found. A procedure to generate consistent chemical signatures using tandem mass spectral libraries of recurrent spectra is proposed. Conlusions Different platforms rendered significantly different metabolite profiles, but the results were highly reproducible when working within one platform. Tandem mass spectral libraries of recurrent spectra are proposed to evaluate the degree of transferability of chemical signatures generated on different platforms. Chemical signatures based on our procedure are most likely cross-platform transferable. Published in 2016. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

A stochastic regression model is presented that separates signal from noise in chemical spectra. Spectra are decomposed into additive contributions from signal and from estimated noise. Numerical results on sample spectra are presented and suggest that this strategy offers an effective and computationally efficient framework for comprehensive noise estimation and analysis. From this analysis more effective methods of feature extraction in chemical spectra can be created. [ABSTRACT FROM AUTHOR]

Enzymes immobilized on solid supports are increasingly used for greener, more sustainable chemical transformation processes. Here, we used microreactors to study enzyme-catalyzed ring-opening polymerization of ϵ-caprolactone to polycaprolactone. A novel microreactor design enabled us to perform these heterogeneous reactions in continuous mode, in organic media, and at elevated temperatures. Using microreactors, we achieved faster polymerization and higher molecular mass compared to using batch reactors. While this study focused on polymerization reactions, it is evident that similar microreactor based platforms can readily be extended to other enzyme-based systems, for example, high-throughput screening of new enzymes and to precision measurements of new processes where continuous flow mode is preferred. This is the first reported demonstration of a solid supported enzyme-catalyzed polymerization reaction in continuous mode. [ABSTRACT FROM AUTHOR]

Abstract: Cells are known to sense and respond to the physical properties of their environment and those of tissue scaffolds. Optimizing these cell–material interactions is critical in tissue engineering. In this work, a simple and inexpensive combinatorial platform was developed to rapidly screen three-dimensional (3D) tissue scaffolds and was applied to screen the effect of scaffold properties for tissue engineering of bone. Differentiation of osteoblasts was examined in poly(ethylene glycol) hydrogel gradients spanning a 30-fold range in compressive modulus (≈10 kPa to ≈300 kPa). Results demonstrate that material properties (gel stiffness) of scaffolds can be leveraged to induce cell differentiation in 3D culture as an alternative to biochemical cues such as soluble supplements, immobilized biomolecules and vectors, which are often expensive, labile and potentially carcinogenic. Gel moduli of ≈225 kPa and higher enhanced osteogenesis. Furthermore, it is proposed that material-induced cell differentiation can be modulated to engineer seamless tissue interfaces between mineralized bone tissue and softer tissues such as ligaments and tendons. This work presents a combinatorial method to screen biological response to 3D hydrogel scaffolds that more closely mimics the 3D environment experienced by cells in vivo. [Copyright &y& Elsevier]

Abstract: The interaction of silica and kaolin with dipalmitoylphosphatidylcholine (DPPC) has been studied using 13C and 31P solid state nuclear magnetic resonance spectroscopy. These studies explore the molecular interactions of these respirable dusts with a model lung surfactant species to characterize silica toxicity in mixed systems. The choline head group of DPPC was found to remain mobile when adsorbed on kaolin, in contrast to an immobile head group on silica. Further, glycerol carbon intensities were greatly diminished relative to that of choline carbons, a result attributed to broadening effects. These preliminary findings suggest that silica toxicity may not be related to choline mobility as previously noted [J. Colloid Interface Sci. 172 (1995) 536–538]. [Copyright &y& Elsevier]

Vibrationally resonant sum-frequency generation (VR-SFG) has been used to characterize the molecular orientation of the phenyl groups at the interface between polystyrene (PS) films and surface-modified glass substrates. Both the interface structure and the film adhesion are found to vary as the substrate surface is changed from hydrophobic to hydrophilic. The improved adhesion on the hydrophilic substrate is attributed to the development of attractive hydrogen bonds between surface hydroxyl (OH) groups and the π electron cloud of the phenyl ring. This interaction is manifest by changes in the orientation distribution of the phenyl rings at the interface. [Copyright &y& Elsevier]

A technique for selective characterization of the structure of free and buried thin-film interfaces by vibrationally resonant sum frequency generation spectroscopy is described. Manipulation of Fresnel coefficients by choice of film thickness on a reflecting substrate allows simultaneous optimization of the signal from the desired interface and minimization of the signal from other interfacial sources. This technique is demonstrated for the free polystyrene (PS)/air and the buried PS/spin-on glass interfaces. Our spectra show that the pendant phenyl group orientation is similar at the buried and free interfaces, with the phenyls pointing away from the bulk PS at each interface. [ABSTRACT FROM AUTHOR]