An investigation of the membranotropicity of the ethylene- and cytokinin-binding proteins from cottonplant shoots by the fluorescent probe method

A. S. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax 627071. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 135–136, January–February, 1994.     

Phosphorylation of cottonplant proteins under the action of protein kinase inhibitors and activators

The occurrence of Ca²⁺-, Ca²⁺-phospholipid-, Ca²⁺-calmodulin-, and cAMP-dependent phosphorylation has been shown with the aid of protein kinase activators and inhibitors and by electrophoresis and autoradiography. Specific substrates have been revealed and it has been demonstrated that the pathways of the realization of the action of cAMP-dependent and Ca²⁺-calmodulin-dependent protein kinases may intersect.A. S. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax 627071. Institute of Nuclear Physics, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax 442603. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 96–100, January–February, 1994.     

Synthesis of a cyclic peptide/protein using the NEXT-A reaction followed by cyclization

By using the NEXT-A reaction, we introduced a non-natural amino acid at the N-terminus of a peptide/protein that contained a cysteine unit. The side chain of the introduced amino acid spontaneously reacted with the cysteine to afford a cyclic peptide/protein.     

Schematic structure of a fragment of the cottonplant lignin macromolecule

A schematic structure has been proposed for an average fragment of the macromolecule of cottonplant dioxane lignin on the basis of the results of a chemical study and quantitative¹H and¹³C NMR spectroscopy.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 234–236, March–April, 1996. Original article submitted June 27, 1994.     

Activation analysis for technetium-99 by the use of a neutron-excitation reaction

The formation of^99mTc was observed when⁹⁹Tc was irradiated by reactor neutrons as a result of the⁹⁹Tc(n, )^99mTc reaction. A good linearity was observed between the activities of^99mTc produced and⁹⁹Tc irradiated. The cross section of the excitation reaction was estimated to be 0.24 b. The application of the nuclear excitation reaction to the activation analysis for low level⁹⁹Tc was studied.     

Synthesis of macrocycles by the ring‐crossover reaction of a cyclic dithioester

The ring‐crossover polymerization of cyclic dithioester 1 was performed in the presence of quaternary onium salts as catalysts at 70–150 °C for 24 h in NMP. It was found that predictable cyclic polymers with the same repeating structures as 1 were obtained with M_ns in the range between 700 and 3,500, quantitatively. It was observed that intermolecular and intramolecular thioester‐exchange reactions proceeded between cyclic monomer 1 and resulting cyclic polymers under thermodynamic control to give a lower‐molecular‐weight cyclic polymer with a lower polydispersity ratio (M_n = 2,400, M_w/M_n = 1.70). © 2006Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 680–687, 2007     

Concise Synthesis of Polysubstituted Carbohelicenes by a C−H Activation/Radical Reaction/C−H Activation Sequence

Disclosed herein is the merging of C?H activation and radical chemistry, enabling rapid access to a structurally diverse family of fused carbohelicenes through the fusion of α‐acetylnaphthalenes with alkynes under oxidative conditions. This cascade process exhibits exquisite chemoselectivity and regioselectivity. The reaction pathway was analyzed by intermediate separations, control experiments, radical trapping, EPR, MALDI‐TOF‐MS, and ESI‐HRMS experiments, and shown to involve a C2?H activation/radical reaction/C8?H activation relay.     

Synthesis of gibbilimbols B and D by a modified Ramberg-Bcklund reaction

Gibbilimbols B and D were synthesized from the facile rearrangement of sulfone in the presence of dibromodifluoromethane and alumina-supported KOH in dichloromethane,followed by refluxing the rearrangement products in conc.HCl and methanol and then treating with thiophenol in the presence of AIBN.     

Activation of cyclic AMP-dependent protein kinase and stimulation of protein phosphorylation in response to adenosine in C-1300 murine neuroblastoma.

DEAE-cellulose chromatography of the 20,000g supernatant fraction of homogenates of C-1300 murine neuroblastoma (clone N2a) yields one major and two minor peaks of cyclic AMP-dependent protein kinase activity. Assessment of the endogenous activation state of the enzyme(s) reveals that the enzyme is fully activated by the treatment of whole cells with adenosine (10 microM) in the presence of the phosphodiesterase inhibitor Ro 20 1724 (0.7 mM). This treatment produces a large elevation in the cyclic AMP content of the cells. The treatment of whole cells with adenosine alone (1-100 microM) or Ro 20 1724 alone (0.1-0.7 mM) produces minimal elevations in cyclic AMP but nevertheless causes significant activations of cyclic AMP-dependent protein kinase. The autophosphorylation of whole homogenates of treated and untreated cells was studied using [gamma-32P] ATP, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Treatments which activate cyclic AMP-dependent protein kinase selectively stimulate the incorporation of 32P into several proteins. This stimulation is most prominent in the 15,000-dalton protein band. The addition of cyclic AMP to phosphorylation reactions containing homogenate of untreated cells stimulates the phosphorylation of the same protein bands. These results indicate that adenosine may have regulatory functions through its effect on the cyclic AMP:cyclic AMP-dependent protein kinase system.     

Negative regulation of a protein tyrosine phosphatase by tyrosine phosphorylation

The low molecular weight protein tyrosine phosphatase (LMW-PTP) is a ubiquitously expressed enzyme with several proposed roles in cell signaling. Previously, two tyrosine phosphorylation modifications of LMW-PTP at sites Tyr-131 and Tyr-132 in response to growth factor stimulation have been mapped and suggested to stimulate LMW-PTP phosphatase activity. Biochemical analysis of tyrosine phosphorylation of a tyrosine phosphatase is challenging because of the intrinsic instability of these modifications. Here we used expressed protein ligation to site-specifically incorporate a phosphotyrosine mimic (phosphonomethylenephenylalanine, Pmp) at the Tyr-131 and Tyr-132 positions and measured the catalytic activity of these semisynthetic LMW-PTPs. The phosphonate-modified LMW-PTPs were 10- to 23-fold less active in dephosphorylating phosphotyrosine peptides derived from the PDGF receptor and p190RhoGap, two putative cellular substrates. These findings suggest the first example of a tyrosine phosphatase that is inhibited by tyrosine phosphorylation and provide a new model for the regulation of LMW-PTP and its role in cell adhesion.     

Copying of RNA Sequences without Pre‐Activation

Template‐directed incorporation of nucleotides at the terminus of a growing complementary strand is the basis of replication. For RNA, this process can occur in the absence of enzymes, if the ribonucleotides are first converted to an active species with a leaving group. Thus far, the activation required a separate chemical step, complicating prebiotically plausible scenarios. Here we show that a combination of a carbodiimide and an organocatalyst induces near‐quantitative incorporation of any of the four ribonucleotides. Upon in situ activation, adenosine monophosphate was found to also form oligomers in aqueous solution. So, both de novo strand formation and sequence‐specific copying can occur without an artificial synthetic step.     

Synthesis of carborane-containing phosphates by catalytic phosphorylation

The catalytic phosphorylation ofo-carboranylmethanol with different phosphorus acid chlorides has been studied. This method makes it possible to obtain esters of phosphorus acids and esters of the corresponding phosphorus acid chlorides containing carboranylmethyl groups. The catalytic phosphorylation of 1,2-bis(hydroxymethyl)-o-carborane affords both acyclic and cyclic phosphate esters. The structure of the synthesizedo-carborano[1,2-e]-1,3,2-dioxaphosphepane was confirmed by X-ray diffraction analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 145–149, January, 1995.     

Analysis of protein phosphorylation by mass spectrometry

Phosphorylation is one of the most frequently occurring post-translational modifications in proteins. In eukaryotic cells, protein phosphorylation on serine, threonine and tyrosine residues plays a crucial role as a modulator of protein function. A comprehensive analysis of protein phosphorylation involves the identification of the phosphoproteins, the exact localization of the residues that are phosphorylated and the quantitation of phosphorylation. In this short review we will summarize and discuss the methodologies currently available for the analysis and full characterization of phosphoproteins with special attention at mass spectrometry-based techniques. In particular, we will discuss affinity-based purification of phosphopeptides coupled to MALDI-TOF analysis, their detection using mass mapping and precursor ion scan, identification of modified sites by MS/MS and quantitation analysis     

Synthesis of aminoindoles by the Bucherer reaction

The reaction of 5-hydroxyindoles with ammonia, alkylamines, or dialkylamines in the presence of sulfites leads to the corresponding 5-aminoindoles. Partial or complete elimination of the substituent is observed in the case of indoles that have an electron-acceptor substituent (COOC₂H₅, COCH₃).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 786–789, June, 1979.