Collagens are integral structural proteins in animal tissues and play key functional roles in cellular modulation. We sought to discover collagen model peptides (CMPs) that would form triple helices and self-assemble into supramolecular fibrils exhibiting collagen-like biological activity without preorganizing the peptide chains by covalent linkages. This challenging objective was accomplished by placing aromatic groups on the ends of a representative 30-mer CMP, (GPO)10, as with L-phenylalanine and L-pentafluorophenylalanine in 32-mer 1a. Computational studies on homologous 29-mers 1a-d (one less GPO), as pairs of triple helices interacting head-to-tail, yielded stabilization energies in the order 1a > 1b > 1c > 1d, supporting the hypothesis that hydrophobic aromatic groups can drive CMP self-assembly. Peptides 1a-d were studied comparatively relative to structural properties and ability to stimulate human platelets. Although each 32-mer formed stable triple helices (CD) spectroscopy, only 1a and 1b self-assembled into micrometer-scale fibrils. Light microscopy images for 1a depicted long collagen-like fibrils, whereas images for 1d did not. Atomic force microscopy topographical images indicated that 1a and 1b self-organize into microfibrillar species, whereas 1c and 1d do not. Peptides 1a and 1b induced the aggregation of human blood platelets with a potency similar to type I collagen, whereas 1c was much less effective, and 1d was inactive (EC50 potency: 1a/1b Ͼ Ͼ 1c > 1d). Thus, 1a and 1b spontaneously self-assemble into thrombogenic collagen-mimetic materials because of hydrophobic aromatic interactions provided by the special end-groups. These findings have important implications for the design of biofunctional CMPs.biomaterial ͉ platelets ͉ structure-function ͉ supramolecular triplex T he self-association of peptides and proteins into well ordered supramolecular structures is of pivotal importance in normal physiology and pathophysiology, such as in the assembly of collagen fibrils (1), actin filaments (2), and amyloid fibrils (3, 4). Collagens, which constitute a ubiquitous protein family in animals, contribute an essential matrix component to soft tissues and bones (5, 6). A structural hallmark of many collagens is a rope-like triple helix, the architecture of which derives from the interplay of three proline-rich polypeptide strands (e.g., two ␣1 and one ␣2 for type I collagen) (6-8). In the core domain of the triple helix, the amino acid sequence G-X-Y is repeated multiple times, and each glycine amide NH forms a hydrogen bond with the X-position amide carbonyl on an adjacent strand. The X-and Y-positions are often populated by L-proline and 4(R)-hydroxy-L-proline (O; Hyp), respectively, with the latter stabilizing the triple helix by stereoelectronic effects (9) and water-bridged hydrogen bonds (10).To investigate collagen's structure and function, researchers have resorted to using synthetic collagen model peptides (CMPs)

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The Multi-Attribute Method (MAM) Consortium was initially formed as a venue to harmonize best practices, share experiences, and generate innovative methodologies to facilitate widespread integration of the MAM platform, which is an emerging ultra-high-performance liquid chromatography–mass spectrometry application. Successful implementation of MAM as a purity-indicating assay requires new peak detection (NPD) of potential process- and/or product-related impurities. The NPD interlaboratory study described herein was carried out by the MAM Consortium to report on the industry-wide performance of NPD using predigested samples of the NISTmAb Reference Material 8671. Results from 28 participating laboratories show that the NPD parameters being utilized across the industry are representative of high-resolution MS performance capabilities. Certain elements of NPD, including common sources of variability in the number of new peaks detected, that are critical to the performance of the purity function of MAM were identified in this study and are reported here as a means to further refine the methodology and accelerate adoption into manufacturer-specific protein therapeutic product life cycles.

Divergence of substrate specificity within the context of a common structural framework represents an important mechanism by which new enzyme activity naturally evolves. We present enzymological and x-ray structural data for hamster chymase-2 (HAM2) that provides a detailed explanation for the unusual hydrolytic specificity of this rodent ␣-chymase. In enzymatic characterization, hamster chymase-1 (HAM1) showed typical chymase proteolytic activity. In contrast, HAM2 exhibited atypical substrate specificity, cleaving on the carboxyl side of the P1 substrate residues Ala and Val, characteristic of elastolytic rather than chymotryptic specificity. The 2.5-Å resolution crystal structure of HAM2 complexed to the peptidyl inhibitor MeOSuc-Ala-Ala-Pro-Ala-chloromethylketone revealed a narrow and shallow S1 substrate binding pocket that accommodated only a small hydrophobic residue (e.g. Ala or Val form an easily identifiable triplet in all known rodent ␣-chymases that can be used to predict elastolytic specificity for novel chymase-like sequences. Phylogenetic comparison defines guinea pig and rabbit chymases as the closest orthologs to rodent ␣-chymases.Chymases (EC 3.4.21.39), serine proteases with a chymotrypsin-fold, are stored within the secretory granules of mast cells along with histamine, tryptases, and other inflammation mediators. When released during mast cell degranulation in various tissues, chymases participate in a variety of biological functions including regulation of vasoactive peptide processing, modulation of inflammatory response, stimulation of submucosal gland secretion, and degradation of extracellular matrix (1). Human chymase has been linked to various pathologic conditions such as allergic inflammatory reactions that can contribute to asthma (2), Crohn disease (3), inflammatory kidney disease (4), and cardiovascular disorders (5, 6).Based on the catalytic triad consisting of His, Asp, and Ser (in that order in the sequence), chymases belong to the S1A family of serine proteases that include, for example, trypsin, chymotrypsin, elastase, and cathepsin G (7, 8). Mammalian chymases divide into two phylogenetic groups, termed ␣-and ␤-chymases (9 -11). The genomes of primates, dogs, ruminants, and rodents apparently contain only one functional ␣-chymase, whereas rodents typically have several ␤-chymases. Until recently, all chymases were thought to possess chymotryptictype substrate specificity, preferring Tyr and Phe (as well as Trp and Leu, to a lesser extent) at the P1 substrate position (Schechter and Berger nomenclature (12)). However, two recent studies have clearly established elastolytic specificity (i.e. preference for small aliphatic residues Ala, Val, and Ile at the P1 position) for mouse chymase-5 (mouse mast cell protease-5; mMCP5) 4 and rat chymase-5 (rMCP5) (13,14). Neither enzyme hydrolyzed a typical chymase substrate with Phe at P1. Site-directed mutagenesis and computer modeling studies suggested Val 216 as a major contributor to this unusual substrate specificity (14).Hamster ch...

Secretory leukocyte protease inhibitor (SLPI) is a protease inhibitor of the whey acidic protein-like family inhibiting chymase, chymotrypsin, elastase, proteinase 3, cathepsin G and tryptase. Performing in vitro enzymatic assays using both Western blotting and liquid chromatography/mass spectrometry techniques we showed that, of the proteases known to interact with SLPI, only chymase could uniquely cleave this protein. The peptides of the cleaved SLPI (cSLPI) remain coupled due to the disulfide bonds in the molecule but under reducing conditions the cleavage can be observed as peptide products. Subsequent ex vivo studies confirmed the presence of SLPI in human saliva and its susceptibility to cleavage by chymase. Furthermore, inhibitors of chymase activity are able to inhibit this cleavage. Human saliva from both normal and allergic individuals was analyzed for levels of cSLPI and a correlation between the level of cSLPI and the extent of allergic symptoms was observed, suggesting the application of cSLPI as a biomarker of chymase activity in humans.

Fragment crystallizable (Fc) region of immunoglobulin G (IgG) antibody binds to specific Fc receptors (FcγRs) to control antibody effector functions. Currently, engineered specific Fc-FcγR interactions are validated with a static conformation derived from the crystal structure. However, computational evidence suggests that the conformational variability of Fcs plays an important role in receptor recognition. Here we elucidate Fc flexibility of IgG1, IgG2, and IgG1 Fc with mutations (M255Y/S257T/T259E) in solution by small-angle X-ray scattering (SAXS). Measured SAXS profiles and experimental parameters show variations in flexibility between Fc isotypes. We develop and apply a modeling tool for an accurate conformational sampling of Fcs followed by SAXS fitting. Revealed conformational variability of the CH2 domain as low as 10 Å in displacement, illustrates the power of the atomistic modeling combined with SAXS. This inexpensive SAXS-based approach offers to improve the engineering of antibodies for tailoring Fc receptor interactions through altering and measuring Fc flexibility.

Determination of drug distribution in brain and other tissues is important in pharmaceutical research. Tissue drug levels need to be determined routinely as they are usually diagnostic for both efficacy and toxicity. Determination of tissue levels in small organ subregions is frequently performed due to important functional considerations. These measurements have traditionally been very tedious requiring extensive dissection and specimen pooling to achieve detection of analytes of interest. Direct and indirect methods utilizing mass spectrometry have been reported for detection of analytes in tissue specimens. Typically, these require very specialized MS or sampling equipment and are only partially successful due to analyte response. We have developed a novel approach for quantitation of tissue sections called Functional Tissue Microanalysis (FTM) in which small circular samples are removed from subregions of interest, extracted and analyzed by conventional LC/MS/MS utilizing electrospray ionization. This allows direct measurement of regional concentrations without dissection and homogenization of tissue specimens as many subregions can be sampled from a single mounted section. Utilization of the FTM approach for analysis of both sagittal and coronal rat brain sections is shown for quantitation of raclopride and rimonabant. Reproducibility of this approach and comparison to conventional methods is reported.

An improved scale-up synthesis was required for the alpha(V)beta(3)/alpha(V)beta(5) integrin antagonist 1, which had demonstrated oral efficacy in eye disease models of angiogenesis and vascular permeability. A stereodefined, quinoline-substituted, unsaturated ester was conveniently prepared by a Suzuki-Miyaura coupling to facilitate exploration of multiple methods of asymmetric reduction. The catalytic chiral hydrogenation of the corresponding unsaturated acid (Z-5b) with a ruthenium-based metal precursor and the (R)-XylPhanePhos ligand proved particularly efficient and economical. The resulting (3S)-quinoline-containing intermediate was reduced to an equal mixture of tetrahydroquinoline diastereomers. The undesired diastereomer could be recycled to the desired one by an oxidation/reduction protocol. The absolute stereochemistry of 1 was established as 3S,3'S by a combination of X-ray diffraction and chemical means.