1.Identification of a highly sulfated fucoidan from sea cucumber Pearsonothuria graeffei with well-repeated tetrasaccharides units.
Hu Y1, Li S1, Li J1, Ye X1, Ding T1, Liu D1, Chen J1, Ge Z2, Chen S3. Carbohydr Polym. 2015 Dec 10;134:808-16. doi: 10.1016/j.carbpol.2015.06.088. Epub 2015 Jul 29.
Sea cucumber fucoidan is a major bioactive component of sea cucumber. The structures of fucoidans have significant influences on their biological activities. The present study clarified the delicate structure of a fucoidan from Pearsonothuria graeffei. Fucoidan was obtained after papain digestion and purified by ion chromatography. The carbohydrate sequence of fucoidan was firstly determined by negative-ion electrospray tandem mass spectrometry (ES-MS) with collision-induced dissociation of the oligosaccharide fragments, which were obtained by mild acid hydrolysis, and completed by NMR for assignment of the anomeric conformation. It was unambiguously identified as a tetrasaccharide repeating unit with a backbone of [ → 3Fuc (2S, 4S) α1 → 3Fucα1→ 3Fuc (4S) α1 → 3Fuc#7 × 10#]n. The glycosidic bonds between the non-sulfated and 2,4-O-disulfated fucose residues were selectively cleaved, and highly ordered oligosaccharide fragments with a tetrasaccharide repeating unit were obtained.
2.The Oncogenic Small Tumor Antigen of Merkel Cell Polyomavirus Is an Iron-Sulfur Cluster Protein That Enhances Viral DNA Replication.
Tsang SH1, Wang R1, Nakamaru-Ogiso E2, Knight SA3, Buck CB4, You J5. J Virol. 2015 Nov 25;90(3):1544-56. doi: 10.1128/JVI.02121-15.
Merkel cell polyomavirus (MCPyV) plays an important role in Merkel cell carcinoma (MCC). MCPyV small T (sT) antigen has emerged as the key oncogenic driver in MCC carcinogenesis. It has also been shown to promote MCPyV LT-mediated replication by stabilizing LT. The importance of MCPyV sT led us to investigate sT functions and to identify potential ways to target this protein. We discovered that MCPyV sT purified from bacteria contains iron-sulfur (Fe/S) clusters. Electron paramagnetic resonance analysis showed that MCPyV sT coordinates a [2Fe-2S] and a [4Fe-4S] cluster. We also observed phenotypic conservation of Fe/S coordination in the sTs of other polyomaviruses. Since Fe/S clusters are critical cofactors in many nucleic acid processing enzymes involved in DNA unwinding and polymerization, our results suggested the hypothesis that MCPyV sT might be directly involved in viral replication. Indeed, we demonstrated that MCPyV sT enhances LT-mediated replication in a manner that is independent of its previously reported ability to stabilize LT.
3.New Ent-Kaurane-Type Diterpene Glycosides and Benzophenone from Ranunculus muricatus Linn.
Wu BL1, Zou HL2, Qin FM3, Li HY4, Zhou GX5. Molecules. 2015 Dec 15;20(12):22445-53. doi: 10.3390/molecules201219801.
Two new ent-kaurane diterpene glycosides, ranunculosides A (1) and B (2), and a new benzophenone, ranunculone C (3), were isolated from the aerial part of Ranunculus muricatus Linn. The chemical structures of compounds 1-3 were established to be (2S)-ent-kauran-2β-ol-15-en-14-O-β-d-glucopyranoside, (2S,4S)-ent-kauran-2β,18-diol-15-en-14-O-β-d-glucopyranoside, and (R)-3-[2-(3,4-dihydroxybenzoyl)-4,5-dihydroxy-phenyl]-2-hydroxylpropanoic acid, respectively, by spectroscopic data and chemical methods. The absolute configuration of 1 was determined by the combinational application of RP-HPLC analysis and Mosher's method.
4.Organomediated Enantioselective (18)F Fluorination for PET Applications.
Buckingham F1, Kirjavainen AK2, Forsback S2, Krzyczmonik A2, Keller T2, Newington IM3, Glaser M3, Luthra SK3, Solin O2, Gouverneur V4. Angew Chem Int Ed Engl. 2015 Nov 2;54(45):13366-9. doi: 10.1002/anie.201506035. Epub 2015 Sep 11.
The first organomediated asymmetric (18)F fluorination has been accomplished using a chiral imidazolidinone and [(18)F]N-fluorobenzenesulfonimide. The method provides access to enantioenriched (18)F-labeled α-fluoroaldehydes (>90% ee), which are versatile chiral (18)F synthons for the synthesis of radiotracers. The utility of this process is demonstrated with the synthesis of the PET (positron emission tomography) tracer (2S,4S)-4-[(18)F]fluoroglutamic acid.
