The tendency of detected amount of peptide types.

<p>The tendency of detected amount of peptide types.</p

The Full MS and MS/MS results of Peptide GAGAGSGAASGAGAGAGAGAGTGSSGFGPY from fresh silk in Table 1.

<p>(A) The full MS data. (B) The b-type and y-type ion fragments of the peptide after CID in MS/MS.</p

Different Types of Peptide Detected by Mass Spectrometry among Fresh Silk and Archaeological Silk Remains for Distinguishing Modern Contamination

<div><p>Archaeological silk provides abundant information for studying ancient technologies and cultures. However, due to the spontaneous degradation and the damages from burial conditions, most ancient silk fibers which suffered the damages for thousands of years were turned into invisible molecular residues. For the obtained rare samples, extra care needs to be taken to accurately identify the genuine archaeological silk remains from modern contaminations. Although mass spectrometry (MS) is a powerful tool for identifying and analyzing the ancient protein residues, the traditional approach could not directly determine the dating and contamination of each sample. In this paper, a series of samples with a broad range of ages were tested by MS to find an effective and innovative approach to determine whether modern contamination exists, in order to verify the authenticity and reliability of the ancient samples. The new findings highlighted that the detected peptide types of the fibroin light chain can indicate the degradation levels of silk samples and help to distinguish contamination from ancient silk remains.</p></div

The detected peptide sequences of silk protein of fresh silk.

<p>All amino acid sequences are from NCBI (20121001). G, A, Y, S, V respectively are the abbreviations of glycine, alanine, tyrosine, serine and valine. The data details of each sample were shown in Supplementary Information (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132827#pone.0132827.s005" target="_blank">S1</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132827#pone.0132827.s006" target="_blank">S2</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132827#pone.0132827.s007" target="_blank">S3</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0132827#pone.0132827.s008" target="_blank">S4</a> Tables).</p><p>The detected peptide sequences of silk protein of fresh silk.</p

Synthesis of Fused Dihydropyrano(furano)pyridines via [4 + 2]-Cycloaddition of 5-Alkenoxy Substituted Oxazoles

A three-step procedure to access fused pyridines has been developed utilizing inexpensive amino acids and alkenols to form the key oxazole precursors. Yields are good to excellent and provide a rapid and inexpensive route to a range of pharmacologically and biologically valuable fused pyridines with difficult to access substitution patterns

Total Synthesis of Ascididemin-Type Alkaloids Using Alkyne Building Blocks

A common approach to ascididemin-type alkaloids, including ascididemin, bromoleptoclinidinone, neocalliactine acetate, and 11-hydroxyascididemin, based on a Brønsted acid-promoted tandem annulation has been developed. Alkyne building blocks were first designed and then employed in alkaloid synthesis; these building blocks can be accessed by a Sonogashira coupling reaction on a multigram scale

Peptide sequences of M436 and M451.

<p>Peptide sequences of M436 and M451.</p

¹⁷O Solid-State NMR as a Sensitive Probe of Hydrogen Bonding in Crystalline and Amorphous Solid Forms of Diflunisal

¹⁷O solid-state NMR (SSNMR) can provide insight into hydrogen bonding interactions in pharmaceutical polymorphs, cocrystals, and amorphous dispersions. When combined with straightforward ¹⁷O synthetic labeling, the use of ¹⁷O SSNMR allows for direct study of key interactions such as hydrogen bonding in these systems. In this work, novel applications of ¹⁷O SSNMR are demonstrated in the analysis of a polymorph of diflunisal, a cocrystal of diflunisal with pyrazinamide, and amorphous dispersions of diflunisal in two polymers. The observation of the ¹⁷O nucleus is shown to be a highly specific and useful alternative to more conventional studies of the ¹H, ¹³C, and ¹⁹F nuclei in these systems and offers unique insight into hydrogen bonding interactions. Quantum chemical calculations are used to assess the ¹⁷O SSNMR measurements for the polymorph of diflunisal for which a crystal structure has been previously determined. Empirical hydrogen bonding trends are then examined in the cocrystal and amorphous solid forms using ¹⁷O NMR parameters. A novel application of ¹H–¹⁷O cross-polarization heteronuclear correlation (CP-HETCOR) experiments is also demonstrated for the cocrystal and two dispersions. This experiment offers specific information about proton environments in proximity to the labeled oxygen sites. The use of ¹⁷O SSNMR techniques extends the utility of SSNMR in applications to cocrystals and amorphous dispersions

Biomolecular Evidence of Silk from 8,500 Years Ago

<div><p>Pottery, bone implements, and stone tools are routinely found at Neolithic sites. However, the integrity of textiles or silk is susceptible to degradation, and it is therefore very difficult for such materials to be preserved for 8,000 years. Although previous studies have provided important evidence of the emergence of weaving skills and tools, such as figuline spinning wheels and osseous lamellas with traces of filament winding, there is a lack of direct evidence proving the existence of silk. In this paper, we explored evidence of prehistoric silk fibroin through the analysis of soil samples collected from three tombs at the Neolithic site of Jiahu. Mass spectrometry was employed and integrated with proteomics to characterize the key peptides of silk fibroin. The direct biomolecular evidence reported here showed the existence of prehistoric silk fibroin, which was found in 8,500-year-old tombs. Rough weaving tools and bone needles were also excavated, indicating the possibility that the Jiahu residents may possess the basic weaving and sewing skills in making textile. This finding may advance the study of the history of silk, and the civilization of the Neolithic Age.</p></div

MS/MS results of Peptide GAGAGAGY.

<p>This figure shows data-dependent acquisition using the LTQ-Orbitrap XL for the peptide at m/z 623.27789 (GAGAGAGY) in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0168042#pone.0168042.t002" target="_blank">Table 2</a> (M451 no. 5). The b- and y-type ion fragments of the peptide after CID in MS/MS.</p