Theoretical Study on the Activity of a-COOH and b-COOH of N-Phosphoryl Aspartic Acids

The bio-mimic reactions of N-phosphoryl amino acids are very important in the study of many biochemical processes. The difference of reactivity between a-COOH and b-COOH in phosphoryl aspartic acid was studied by theoretical study (Hartree-Fock and Density Functional methods) in this paper. The intermediates II containing five-membered ring were more stable than III with six-membered ring. While for intermediates III, the isomers with six-membered ring in apical-equatorial spanning arrangement were more stable than those with di-equatorial spanning arrangement. At B3LYP/6-31G** level, it was shown that transition states IV and V involving a-COOH or b-COOH group had energy barriers of DE = 58.67 kJmol-1 and 103.94 kJmol-1, respectively. These results were in agreement with the experimental data. So the a-COOH group was involved in form of the intramolecular penta-coordinate phosphoric-carboxylic mixed anhydride intermediates, but not b-COOH group.

Synthesis and Biological Activities of N-Phosphoryl Branched Peptides

A series of N-phosphoryl branched peptides were synthesized by coupling of various N-phosphoryl amino acids to L-Lysine methyl ester, and their structures were confirmed by 31P NMR, 1H NMR, MS and elemental analysis. The results of cell biological tests indicated that compound 1d and 1e obviously inhibited the growth of both K562 and A2780 cells.

INTRAMOLECULAR β-CARBOXYLIC ACTIVATING OF N-PHOSPHORYL ASPARTIC ACID

The β-carboxylic group plays an important role in the peptide formation,esterification and the ester exchange at the phosphoryl group of N-phosphorylated aspartic acid.

Interaction between N-phosphoryl-α-,β-and γ-amino acids and nucleosides

The reactions of four different N-（O,O＇-diisopropyl） phosphoamino acids （DIPP-aa）, such as N-phosphoryl-L-α-alanine （DIPP- L-α-Ala）, N-phosphoryl-D-α-alanine （DIPP-D-α-A1a）, N-phosphoryl-β-alanine （DIPP-β-A1a） and N-phosphoryl-γ-amino butyric acid （DIPP-γ-Aba）, and four nucleosides, adenosine （A）, guanosine （G）, cytidine （C） and uridine （U）, were studied by electrospray ionization tandem mass spectrometry （ESI-MS/MS） and HPLC/ESI-MS. DIPP-L-α-A1a and DIPP-D-α-A1a produced the same phosphorylated nucleosides, dinucleotides and phosphoroligopeptide. However, DIPP-β-A1a and DIPP-γ-Aba gave no relevant products.

RNA Cleavage by N-Phosphoryl Serine in Histidine Buffer

In the presence of histidine, N-(O,O-diisopropyl)phosphoryl serine could catalyze the cleavage of RNA in aqueous solution at neutral pH. The results were detected by sub-marine agarose gel electrophoresis and capillary zone electrophoresis. It was found that at high concentration histidine could cleave the RNA slightly. While the participation of DIPP-Ser could significantly accelerate the cleavage reaction. N-phosphodipeptide---N-(O,O-diisopropyl) Ser-His are proposed to be involved in the mechanism.

Oligouridylates Formation with N-(O,O'-Diisopropyl)-Phosphoryl Alanine in the presence of Poly(β-(N^7-Adeninyl)Ethyl Methacrylate)

The oligouridylates formation with N-(O,O-diisopropyl)-phosphoryl alanine in the presence of poly((-(N7-adeninyl)ethyl methacrylate) was studied. An increased yield by the presence of the polymeric nucleic acid analog was confirmed by anion exchange column HPLC, C18 reverse phase HPLC, and turbo ionspray MS.

Orientation of the peptide formation of N-phosphoryl amino acids in solution

The peptide formation of N-phosphoryl aminoacids with amino acids proceeds in aqueous solution withoutany coupling reagents. After being separated in sephadex gelcolumn, the phosphoryl dipeptides were analyzed by theelectrospray ionization tandem mass spectrometry (ESIMS/MS). The result demonstrates that phosphoryl dipeptideswere datected in all the reaction systems. It is found tkat theformation of N-phosphoryl dipeptides is oriented: theN-terminal amino acid residues of the N-phosphoryl dipep-tides are from N-phosphoryl amino acids, and the peptideelongation happened at the C-terminal. Only adipeptide, noβ-dipeptide, is formed in the N-phosphoryl dipeptides,showing that α-carboxylic group is activated selectively byN-pbosphorylation. Theoretical calculation shows that thepeptide formation of N-phosphoryl amino acids might hap-pen through a pentu-coordinate carboxylic-phosphoric in-termediate in solution. These results might give some clues tothe stlidy on the origin of proteins and protein

Hydrolysis Reaction of N-Phosphoryl-α-, β- and γ-amino Acids Studied by HPLC

The hydrolysis reactions of N-（O,O＇diisopropyl）phosphoryl-L-α-alanine （DIPP-L-α-Ala）, N-（O,O＇diisopropyl）- phosphoryl-D-α-alanine （DIPP-D-α-Ala）, N-（O,O＇-diisopropyl）phosphoryl-β-alanine （DIPP-β-Ala） and N-（O,O＇-diisopropyl）phosphoryl-γ-amino butyric acid （DIPP-γ-Aba）, were studied by HPLC and their hydrolysis reaction kinetic equations were obtained. Under acid conditions, the reaction rate of DIPP-L-α-Ala was close to that of DIPP-D-α-Ala and the same rule was true between DIPP-β-Ala and DIPP-γ-Aba. Meantime, the reaction rate of DIPP-L/D-α-Ala was as 10 times as that of DIPP-β-Ala or DIPP-γ-Aba. Under basic conditions, the hydrolysis reactions of DIPP-β-Ala and DIPP-γ-Aba almost did not take place and the reaction rate of DIPP-L/D-α-Ala was about 1/10 of that under acid conditions. Moreover, theoretical calculation further illuminated the differences of the hydrolysis rate from the view of energy. The results would provide some helpful clues to why nature chose a-amino acids but not other kinds of analogs as protein backbones.

Elucidation of O-Phosphoryl and N-Phosphoryl Amino Acids by Electrospray Ionization Tandem Mass Spectrometry

Mass spectroscopic characteristics of phosphoryl amino acids were studied in detail by positive and negative electrospray ionization mass spectrometry (ESI-MS) in conjunction with tandem mass spectrometry (MS/MS). Be- sides N-diisopropyloxyphosphoryl amino acids (N-DIPP-AA), O-phospho- and O-diisopropyloxyphosphoryl amino acids (O-DIPP-AA) were studied and compared to N-DIPP-AA. The fragmentation pathways of [M+H]+, [M+Na]+ and [M-H]- ions of phosphoryl amino acids were summarized. In addition to several similar patterns, each of them showed its characteristic fragmention.

Interactions of oxidative radicals with N-phosphoryl dipeptide derivatives

The interactions of oxidative radicals (Br2?-, HO?etc.) with N-phosphoryl dipeptide derivatives (NDM-TrpOMe and NDT-MetOMe) have been investigated by using pulse radiolysis at different pH values. It has been found that Br2?- and HO? radicals oxidize the Met-site and Trp-site in the dipeptide derivatives via formation of the three-electron-bonded intermediate and indolyl radical simultaneously. Then the intramolecular electron transfer along the peptide backbone occurs. The rate constants of electron transfer, k, have been determined and the reaction mechanism has been deduced.

Widespread arginine phosphorylation in human cells——a novel protein PTM revealed by mass spectrometry

Arginine phosphorylation(p Arg)is recently discovered as a ubiquitous protein N-phosphorylation in bacteria.However,its prevalence and roles in mammalian cells remain largely unknown due to the lack of established workflow and the inherent lability of phosphoramidate(P–N)bond.Emerging evidences suggest that N-phosphorylation may extensively exist in eukaryotes and play crucial roles.We report a phosphoproteomic workflow,which allows for the first time revealing the widespread occurrence of p Arg in human cells by mass spectrometry.By virtue of this approach,we identified 152 high-confidence p Arg sites derived from 118 proteins.Remarkably,the discovered p Arg phosphorylation motif and gene ontology hint a possible cellular function of arginine phosphorylation which may regulate the favorability of propeptide convertase substrate.The obtained p Arg dataset paves a way for a better understanding of the biological functions of eukaryotic p Arg in the future.

Isolation and identification of phosphorylated lysine peptides by retention time difference combining dimethyl labeling strategy

Protein phosphorylation plays essential roles in various biological procedures. Despite the well-established enrichment strategies for O-phosphoproteomics, the intrinsic acid lability of N–P phosphoramidate bond(phosphorylation of histidine, arginine and lysine) has impaired the progress of N-phosphoproteomics. Herein, we reported a retention time difference combining dimethyl labeling(ReDD) strategy for the isolation and identification of phosphorylated lysine(pLys) peptides. By such a method, pLys peptide could be isolated under 100000-fold interference of non-phosphorylated peptides. Furthermore, ReDD strategy was applied to map pLys sites from E. coli samples, leading to the identification of 11 pLys sites, among which K26p that originating from autonomous glycyl radical cofactor was validated both in mass spectrometry and HPLC co-elution experiments. Furthermore, 112 pLys sites from 100 proteins were identified in HeLa cells. All these results demonstrate that ReDD could provide a first glimpse into Lys phosphorylation, and could be an important step toward the global perspective on protein phosphorylation.

The Regulation Effect of Phosphoryl Group on Amino Acid Side Chain

The amino acids’ side chains act as the relay device to modulate the chemical reactivity of the N-phosphoryl amino acids. The N-dialkyl phosphoryl cysteine is stable, but the N-dialkyl phosphoryl serine or threoine was converted into many kinds of products at 40℃. The N-dialkyl phosphoryl gltamic acid is a stable compound, while the N-dislkyl phosphoryl aspartic acid was transferred into the peptides, esters and the phosphoryl ester-exchanged products under mild conditions. The N-dialkyl phosphoryl histidine has the similar reactivity through the co-participation of the side chain, carboxyl and phosphoryl groups. A hexacoordinate phosphorus was proposed to account for this differentiation and promotion effect.

LC-MS analysis of the formed peptides from N-(O,O-diiso-propyl)phosphoryl aspartic acid

LC-ESI-MS method was used to analyze the formed di and tri-peptide in the reaction system of N-(O, O-diisopropyl) phosphoryl aspartic acid and adenosine. Cluster ions of the peptides were given in the ESI-MS. The structures of these small peptides were confirmed by LC-MS-MS analysis. Compared with the traditional HPLC-UV detection, this method showed good sensitivity and selectivity for peptide in the presence of compounds with strong UV absorption, such as nucleoside and nucleotide.