The systematic and in-depth study of phosphoproteome rely on highly reproducible and specific phosphopeptide enrichment methods. At present, a variety of enrichment methods have been developed based on different principles, and these methods often display different selectivity and specificity. It is therefore very important to select the most suitable enrichment method according to different research purposes. This review summarized the phosphopeptide enrichment based on affinity chromatography, immunoprecipitation, chemical derivatization, chromatography and other newly developed methods. The advantages and disadvantages of these methods, as well as the related optimization and improvement strategies, were discussed in detail. In addition, we also briefly summarized the progress of the combination of phosphopeptide enrichment and fractionation methods developed in recent years.
Phosphopeptides/metabolism* ; Proteomics/methods* ; Titanium/chemistry* ; Chromatography, Affinity ; Proteome ; Phosphorylation

OBJECTIVETo investigate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on the stability of resin-dentin bonds against pH cycling.

METHODSResin-bonded dentin specimens were prepared following manufacturers' instructions, and randomly divided into 3 groups. Among them, 2 groups experienced pH cycling, in which specimens applied CPP-ACP or distilled and deionized water (DDW) on the bonding interface, respectively. Microtensile bond strength (muTBS) testing, failure mode analysis, micromorphological and nanoleakage evaluation of bonding interface and elemental analysis within hybrid layer were performed after 15 days pH cycling. The other group was tested immediately after specimens' preparation without pH cycling.

RESULTSNo significant differences were found in muTBS between no pH cycling and pH cycling/CPP-ACP group. Their muTBS were both significantly higher than that of pH cycling/DDW group (P < 0.05). Mixed fractures were the most prevalent failure mode. The quality of hybrid layer in pH cycling/CPP-ACP group was better than that of pH cycling/DDW group, and the nanoleakage was also less severe. Comparing with pH cycling/DDW group, the atomic percentages of Ca in the other two groups were both significantly higher, while those of Ag were statistically lower (P < 0.05).

CONCLUSIONLocal application of CPP-ACP can promote the stability of resin-dentin bonding interface against pH cycling and prolong bonding degeneration.

Calcium Phosphates ; Caseins ; Dental Bonding ; Dentin ; Dentin-Bonding Agents ; Humans ; Phosphopeptides ; Resin Cements

The phosphorylation is one of most common protein post-translational modifications. The protein phosphorylation plays important roles in the life through the reversible process of phosphorylation and dephosphorylation by kinases and phosphatases. Systematical analysis of the phosphorylation state of proteins would greatly help to reveal the mystery of the life. Recently, with the development of mass spectrometer, bioinformatics sortwares and enrichment methods of phosphopeptides, phosphorylation stduy of orgnism proteins by mass spectrometer has become mature gradually. Liver is one of the most important metabolic and immune organs. In-depth study of protein phosphorylation in liver is of great importance to reveal its function. And booming phosphoproteomics has been applied into the study of liver, which has deepened the knowledge of molecular mechnism of its physiology and pathology states. Here, we review the recent progress on the research and development of phosphoproteomics and their application in liver proteomics study.
Computational Biology ; Humans ; Liver ; metabolism ; pathology ; physiology ; Mass Spectrometry ; Phosphopeptides ; metabolism ; Phosphorylation ; Protein Processing, Post-Translational ; Proteomics

OBJECTIVETo screen phosphopeptide specific for acute leukemia.

METHODSMononuclear cells from bone marrow were collected from 16 newly diagnosed acute lymphoblastic leukemia (ALL) and 20 acute myeloid leukemia (AML) patients. Peptides were extracted and purified, analyzed by immunoprecipitation and liquid chromatography coupled with tandem mass spectrometry (LC-MS).

RESULTS(1) Non-receptor tyrosine kinase family members Fyn, Yes, Src widely expressed in acute leukemia; (2) Some phosphopeptides, including non-receptor tyrosine kinase family members Abl/iso1 and Abl, non-receptor Ser/Thr protein kinase family members Bcr, JNK2, JNK2 iso2, Adaptor/scaffold members Cas-L, Cbl, CrkL CENTD1 (Centaurin delta1) ZO2, transcriptor GFR-1 and phosphatase SHIP-2 were detected in Ph positive ALL, but not in other kinds of ALL. (3) Hck, Lyn and Fgr selectively expressed in AML (except AML-M(3)).

CONCLUSIONSome phosphopeptides were specific for ALL and AML, and may be useful for diagnosis and therapy of acute leukemia.

Chromatography, High Pressure Liquid ; Humans ; Immunoprecipitation ; Leukemia, Myeloid, Acute ; genetics ; metabolism ; Neoplasm Proteins ; analysis ; Phosphopeptides ; analysis ; Phosphorylation ; Precursor Cell Lymphoblastic Leukemia-Lymphoma ; genetics ; metabolism ; Proteomics ; Tandem Mass Spectrometry

The C-terminal domain of RNA polymerase II is an unusual series of repeated residues appended to the C-terminus of the largest subunit and serves as a flexible binding scaffold for numerous nuclear factors. The binding of these factors is determined by the phosphorylation patterns on the repeats in the domain. In this study, we generated a synthetic antibody library by replacing the third heavy chain complementarity-determining region of an anti-HER2 (human epidermal growth factor receptor 2) antibody (trastuzumab) with artificial sequences of 7–18 amino-acid residues. From this library, antibodies were selected that were specific to serine phosphopeptides that represent typical phosphorylation patterns on the functional unit (YSPTSPS)₂ of the RNA polymerase II C-terminal domain (CTD). Antibody clones pCTD-1stS2 and pCTD-2ndS2 showed specificity for peptides with phosphoserine at the second residues of the first or second heptamer repeat, respectively. Additional clones specifically reacted to peptides with phosphoserine at the fifth serine of the first repeat (pCTD-1stS5), the seventh residue of the first repeat and fifth residue of the second repeat (pCTD-S7S5) or the seventh residue of either the first or second repeat (pCTD-S7). All of these antibody clones successfully reacted to RNA polymerase II in immunoblot analysis. Interestingly, pCTD-2ndS2 precipitated predominately RNA polymerase II from the exonic regions of genes in genome-wide chromatin immunoprecipitation sequencing analysis, which suggests that the phosphoserine at the second residue of the second repeat of the functional unit (YSPTSPS)2 is a mediator of exon definition.
Antibodies ; Chromatin Immunoprecipitation ; Clone Cells ; Complementarity Determining Regions ; DNA-Directed RNA Polymerases* ; Exons* ; Peptides ; Phosphopeptides ; Phosphorylation* ; Phosphoserine ; Receptor, Epidermal Growth Factor ; RNA Polymerase II* ; RNA* ; Sensitivity and Specificity ; Serine

Adenomatous Polyposis Coli Protein ; chemistry ; metabolism ; Amino Acid Sequence ; Chromatography, High Pressure Liquid ; HeLa Cells ; Humans ; Kinesin ; chemistry ; metabolism ; Microtubule-Associated Proteins ; chemistry ; metabolism ; Microtubules ; metabolism ; Molecular Sequence Data ; Phosphopeptides ; analysis ; Phosphorylation ; Protein Multimerization ; Tandem Mass Spectrometry

Polo-box domain 1 (PBD1) is a characteristic domain of polo-like kinase 1 (PLK1), which locates in C-terminal and can influence the catalytic activity and specific subcellular locations of PLK1. At present, most PLK1 inhibitors are developed to occupy the ATP pocket or its close sites. However, this kind of PLK1 inhibitors is difficult to pursue target selectivity and may encounter cross drug resistance with other kinase inhibitors due to the conserved sequence of ATP pocket. Recently, PBD1, with aberrant specificity in sequence and structure, has attracted enormous interests as the alternative target to the discovery of corresponding inhibitors for anti-tumor drugs. The structure and function of PBD1 as well as the advances of its inhibitors are reviewed in this paper.
Benzocycloheptenes ; chemistry ; pharmacology ; Benzoquinones ; chemistry ; pharmacology ; Cell Cycle Proteins ; antagonists & inhibitors ; chemistry ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Humans ; Indole Alkaloids ; chemistry ; pharmacology ; Lactams ; chemistry ; pharmacology ; Peptides, Cyclic ; chemistry ; pharmacology ; Phosphopeptides ; chemistry ; pharmacology ; Protein-Serine-Threonine Kinases ; antagonists & inhibitors ; chemistry ; Proto-Oncogene Proteins ; antagonists & inhibitors ; chemistry