The natural sepia pigment is based on eumelanin, the most prevalent type of melanin, and can be obtained from the ink sac of different members of the Cephalopoda class, such as cuttlefish and squid. The main components of natural sepia are indole derivatives, but pigments prepared following historical recipes are generally more heterogeneous as they may also contain proteins, polysaccharides, and lipids. Sepia is difficult to identify in works of art owing to its heterogeneity, insolubility in most organic solvents, interference by the binding media, and its poorly defined spectroscopic properties. In the present study, three commercial natural sepia pigments, along with a sample extracted from cuttlefish following a historical recipe in an artists' manual, a relatively more pure commercial melanin, and a synthetic eumelanin obtained by the oxidation of dopamine were characterized by normal Raman and surface‐enhanced Raman scattering (SERS), complemented by Fourier transform infrared, pyrolysis–gas chromatography–mass spectrometry, and X‐ray fluorescence, in order to obtain vibrational signatures for the identification of the pigment in works of art. Pyrolysis–gas chromatography–mass spectrometry and X‐ray fluorescence analysis showed that the pigment composition is strongly influenced by the extraction procedure used. Lipids were identified in the chromatograms of all the natural samples analyzed, and the majority of these also showed the presence of cholesterol derivatives. Additional components resulting from the decomposition of polysaccharides were found to be present in the sepia extracted from cuttlefish in our laboratories. Normal Raman and SERS were also used to study two sepia inks applied on paper and subjected to accelerated aging. In the SERS measurements, a hydroxylamine‐reduced silver colloid was used as this substrate is suitable for the identification of other natural heterogeneous black‐brown pigments. The SERS methodology developed was applied to identify sepia in Waiting for Aaron, a drawing by the 19th century artist Robert Frederick Blum. Copyright © 2014 John Wiley & Sons, Ltd.

The building blocks of a virus derived from de novo biosynthesis during infection and/or catabolism of preexisting host cell biomass, and the relative contribution of these 2 sources has important consequences for understanding viral biogeochemistry. We determined the uptake of extracellular nitrogen (N) and its biosynthetic incorporation into both virus and host proteins using an isotope-labeling proteomics approach in a model marine cyanobacterium Synechococcus WH8102 infected by a lytic cyanophage S-SM1. By supplying dissolved N as 15N postinfection, we found that proteins in progeny phage particles were composed of up to 41% extracellularly derived N, while proteins of the infected host cell showed almost no isotope incorporation, demonstrating that de novo amino acid synthesis continues during infection and contributes specifically and substantially to phage replication. The source of N for phage protein synthesis shifted over the course of infection from mostly host derived in the early stages to more medium derived later on. We show that the photosystem II reaction center proteins D1 and D2, which are auxiliary metabolic genes (AMGs) in the S-SM1 genome, are made de novo during infection in an apparently light-dependent manner. We also identified a small set of host proteins that continue to be produced during infection; the majority are homologs of AMGs in S-SM1 or other viruses, suggesting selective continuation of host protein production during infection. The continued acquisition of nutrients by the infected cell and their utilization for phage replication are significant for both evolution and biogeochemical impact of viruses.

We present an analytical strategy, dimethylation-deuteration and oxygen-exchange IPTL (diDO-IPTL), for high-precision, broad-coverage quantitative proteomics. The diDO-IPTL approach combines two advances in isobaric peptide terminal labeling (IPTL) methodology: first, a one-pot chemical labeling strategy for attaching isotopic tags to both the N- and C-termini of tryptic peptides, and second, a search engine (based on the Morpheus algorithm) optimized for identification and quantification of twinned peaks from peptide fragment ions in MS spectra. The diDO-IPTL labeling chemistry uses only high-purity, relatively inexpensive isotopic reagents (O water and deuterated formaldehyde) and requires no postlabeling cleanup or isotopic impurity corrections. This strategy produces proteome-scale relative quantification results with high accuracy and precision, suitable for the detection of small protein abundance variations between complex biological samples. In a two-proteome mixture experiment, diDO-IPTL quantification discriminates 1.5-fold changes in abundance of over 1000 proteins with 88% accuracy. The diDO-IPTL methodology is a high-precision, economical approach to quantitative proteomics that is applicable to a wide variety of sample types.

Decades of technological and methodological advances in Raman spectroscopy have brought this technique from laboratory innovation to a well-established analytical tool with increasing applicability to the study of cultural heritage objects. Enduring research in the field of miniaturization has given rise to new generations of mobile, portable, and handheld spectrometers that have deeply transformed the way in which scientists approach materials analysis. Although sometimes limited in terms of performance and flexibility compared with their benchtop counterparts, miniaturized instruments are typically compact and light, user-friendly, and equipped with fiber optics and batteries, thus

The cover image is based on the Research Article Evaluation and optimization of the potential of a handheld Raman spectrometer: in situ, noninvasive materials characterization in artworks by Federica Pozzi et al., https://doi.org/10.1002/jrs.5585.