Comparative transcriptome and metabolome profiles of the leaf and fruits of a Xianjinfeng litchi budding mutant and its mother plant.

Background: Litchi (Litchi chinensis) is an important sub-tropical fruit in the horticulture market in China. Breeding for improved fruit characteristics is needed for satisfying consumer demands. Budding is a sustainable method for its propagation. During our ongoing breeding program, we observed a litchi mutant with flat leaves and sharp fruit peel cracking in comparison to the curled leaves and blunt fruit peel cracking fruits of the mother plant. Methods: To understand the possible molecular pathways involved, we performed a combined metabolome and transcriptome analysis. Results: We identified 1,060 metabolites in litchi leaves and fruits, of which 106 and 101 were differentially accumulated between the leaves and fruits, respectively. The mutant leaves were richer in carbohydrates, nucleotides, and phenolic acids, while the mother plant was rich in most of the amino acids and derivatives, flavonoids, lipids and organic acids and derivatives, and vitamins. Contrastingly, mutant fruits had higher levels of amino acids and derivatives, carbohydrates and derivatives, and organic acids and derivatives. However, the mother plant's fruits contained higher levels of flavonoids, scopoletin, amines, some amino acids and derivatives, benzamidine, carbohydrates and derivatives, and some organic acids and derivatives. The number of differentially expressed genes was consistent with the metabolome profiles. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway-enriched gene expressions showed consistent profiles as of metabolome analysis. Conclusion: These results provide the groundwork for breeding litchi for fruit and leaf traits that are useful for its taste and yield.

[Intervention effects of erythropoietin derived peptide (HBSP) on renal injury induced by acute skeletal muscle strain in rats].

Objective: To investigate the protective effects of erythropoietin derived peptide, also known as spiral B surface peptide (HBSP), on kidney and aggregated proteins (Agrin) levels in acute skeletal muscle strain rats. Methods: Forty SPF grade SD male rats were randomly divided into control group, injury group, HBSP group and EPO group, with 10 rats in each group. Acute skeletal muscle strain animal models were established except the control group. After successful modeling, the rats in HBSP group and EPO group were intraperitoneally injected with 60 µg/kg HBSP and 5 000 U/kg recombinant human erythropoietin (rhEPO), and the rats in the control group and the injured group were intraperitoneally injected with 0.9% normal saline. Renal function was monitored with relevant kits; Hematoxylin-eosin staining was used to observe the pathological morphology of kidney tissue and skeletal muscle strain tissue. The apoptosis rate of renal tissue cells was detected by in situ terminal transferase labeling (TUNEL). Western blot and quantitative polymerase chain reaction (Q-PCR) were used to determine the expressions of Agrin and muscular-specific kinase (MuSK) in the injured skeletal muscle of rats in each group. Results: Compared with the control group, the renal function indexes serum creatinine (Cr), urea nitrogen (BUN) and 24 h urinary protein (UP24) levels of rats in injured group were increased (P＜ 0.05), but the levels of BUN, Cr and UP24 of rats in HBSP group were decreased (P＜0.05). Compared with HBSP group, there were no significant differences in the above indexes in EPO group (P＞0.05). In the control group, the muscle fiber structure was intact, the shape and structure of the fiber bundles were normal, and there was no infiltration of red blood cells and inflammatory cells in the interstitium, and no fibrohyperplasia. In the injured group, the muscle tissue showed sparse and irregular arrangement, and the interstitial widened with a large number of inflammatory cells and red blood cell infiltration. Erythrocytes and inflammatory cells were reduced in HBSP group and EPO group, and the transverse and longitudinal lines of muscle were clear. The glomerular structure of the rats in the fibrohyperplasia control group was intact and no lesions were observed. In the injured group, glomerular hypertrophy and significant matrix hyperplasia were observed, as well as the expansion of renal cysts with vacuolar and significant inflammatory infiltration were observed, and the inflammatory infiltration was reduced in the HBSP and EPO groups. Glomerular hypertrophy and hyperplasia were alleviated. The apoptosis rates of kidney cells in control group, injured group, HBSP group and EPO group were (4.05±0.51) %, (26.30±2.05) %, (14.28±1.62) % and (16.03±1.77) %, respectively, and there were significant differences among these groups (P＜0.05). Compared with control group, the levels of Agrin and MuSK in skeletal muscle pulled tissue were significantly decreased (P＜0.05), and those of HBSP group and EPO group were significantly increased compared with injured group (P＜0.05), but there was no significant difference between HBSP group and EPO group (P＞0.05). Conclusion: Erythropoietin derived peptide (HBSP) has obvious intervention effects on renal function injury in rats with acute skeletal muscle strain, and its mechanisms may be related to reducing the apoptosis rate of renal tissue cells and activating Agrin and MuSK expression.

Synthesis, Characterization, and Pharmacodynamics Study of Enrofloxacin Mesylate.

INTRODUCTION: Enrofloxacin is used in the treatment of a wide variety of bacterial infections in mammals. However, its poor solubility limits the clinical use. METHODS: In order to improve the solubility of enrofloxacin, the enrofloxacin mesylate (EM) were obtained by a chemical synthesis method. The characterization of EM was carried out using ultraviolet scan (UV), synchronous thermal analysis (SDT), fourier transform infrared spectrometer (FTIR) and mass spectrometry (MS), nuclear magnetic resonance (NMR) and X-ray powder diffraction analysis (XRPD). Acute toxicity of EM in Kunming mice was studied. Besides, pharmacokinetic studies were performed in New Zealand rabbits at a single oral dose of 10 mg/kg, and the antibacterial activity of EM was also evaluated. RESULTS: EM was successfully synthesized and purified. The stoichiometric ratio of mesylate to enrofloxacin was 1:1 and the aqueous solubility of EM was 483.01±4.06 mg/mL, the solubility of EM was about 2000 times higher than enrofloxacin. The oral lethal dose (LD50) of EM was 1168.364 mg/kg, and the pharmacokinetics indicated that the oral relative bioavailability of EM was about 1.79 times and 1.48 times higher than that of enrofloxacin and enrofloxacin hydrochloride, respectively. In addition, the in vitro antibacterial activity of EM was not significantly changed compared with enrofloxacin and enrofloxacin hydrochloride. CONCLUSION: EM has higher solubility, low toxicity for oral use, and increases the oral bioavailability in rabbit. This study may be of benefit for the development of new enrofloxacin drugs.

Process service quality evaluation based on Dempster-Shafer theory and support vector machine.

Human involvement influences traditional service quality evaluations, which triggers an evaluation's low accuracy, poor reliability and less impressive predictability. This paper proposes a method by employing a support vector machine (SVM) and Dempster-Shafer evidence theory to evaluate the service quality of a production process by handling a high number of input features with a low sampling data set, which is called SVMs-DS. Features that can affect production quality are extracted by a large number of sensors. Preprocessing steps such as feature simplification and normalization are reduced. Based on three individual SVM models, the basic probability assignments (BPAs) are constructed, which can help the evaluation in a qualitative and quantitative way. The process service quality evaluation results are validated by the Dempster rules; the decision threshold to resolve conflicting results is generated from three SVM models. A case study is presented to demonstrate the effectiveness of the SVMs-DS method.

Effects of rosuvastatin correlated with the down-regulation of CYP4A1 in spontaneously hypertensive rats.

The effects of long-term rosuvastatin treatment on the regulation of cytochrome P450 (CYP) 4A1 expression and vascular homeostasis of spontaneously hypertensive rat (SHR) are still unknown. In this study SHRs were randomly divided into three groups (n=10 per group): SHR group, H-Rv group (rosuvastatin 2.5 mg·kg(-1)·d(-1)), L-Rv group (rosuvastatin 0.5 mg·kg(-1)·d(-1)), and 10 male Wistar-Kyoto (WKY) rats in the control group (WKY group). All rats were treated with rosuvastatin for 12 weeks. The systolic blood pressure (SBP), left ventricle weight index (LVWI) and plasma lipids were measured during or after treatment. The expression of CYP4A1 mRNA and protein in different tissues was detected by real-time PCR and Western blot. In the heart, kidney and aorta, the CYP4A1 expressions were down-regulated at both mRNA and protein levels in rosuvastatin-treated groups compared with the untreated SHR group (P<0.05 or P<0.01), and high-dose rosuvastatin exerted a stronger down-regulatory effect. The increasing trend of blood pressure was markedly blunted in the rosuvastatin-treated groups versus the untreated SHR group, and a stronger effect was observed in high-dose group (P<0.05 and P<0.01 at different time points). LVWI, an indicator of ventricle hypertrophy, was improved in the high-dose group compared with the untreated SHR group (P<0.05). The plasma concentrations of TC, TG and LDL-C in three SHR groups (high-dose, low-dose and untreated group) were all significantly lower than those of WKY group (P<0.05 or P<0.01), which seemed unrelated to the treatment of rosuvastatin. These findings suggested that hypertension in SHRs was possibly associated with CYP4A1 overexpression, and the effects of rosuvastatin on blood pressure and ventricle hypertrophy were potentially correlated with CYP4A1 and its metabolite other than lipid profiles. Multiple mechanisms are likely involved in the beneficial effects of statins with respect to the regulation of CYP4A1.

Construction of multifunctional modules for drug discovery: synthesis of novel thia/oxa-azaspiro[3.4]octanes.

New classes of thia/oxa-azaspiro[3.4]octanes are synthesized through the implementation of robust and step-economic routes. The targeted spirocycles have been designed to act as novel, multifunctional, and structurally diverse modules for drug discovery. Furthermore, enantioselective approaches to the spirocycles are reported.

Regulation on RhoA in vascular smooth muscle cells under inflammatory stimulation proposes a novel mechanism mediating the multiple-beneficial action of acetylsalicylic acid.

Recent studies have revealed the additional beneficial effects of acetylsalicylic acid (aspirin) in the medication of cardiovascular diseases. The small GTPase RhoA as an important signaling factor is implicated in a wide range of cell functions. This study aimed to investigate the regulatory effect of acetylsalicylic acid on RhoA in vascular smooth muscle cells (VSMCs). We found that aspirin at 300 µM suppressed VSMCs proliferation stimulated by LPS, and this inhibitory effect was partially mediated by inhibiting the iNOS/NO pathway. RhoA overexpression was downregulated by aspirin (both 30 and 300 µM) because of enhanced degradation of RhoA protein. The effect of LPS on increasing active RhoA level was significantly attenuated by aspirin (300 µM), which exerted no effect on RhoA translocation. The promoted RhoA phosphorylation under LPS stimulation, coupled with RhoA protein expression, was greatly decreased by aspirin treatment. No effect of aspirin was found on the expression, activation, and phosphorylation of RhoA in VSMCs devoid of inflammatory stimulation. Our investigation indicates that the regulation of RhoA by aspirin in VSMCs under inflammatory stimulus could be a novel mechanism via which aspirin, apart from the COX-dependent action, exerted the multiple beneficial effects.

Heregulin-ß1-induced GPR30 upregulation promotes the migration and invasion potential of SkBr3 breast cancer cells via ErbB2/ErbB3-MAPK/ERK pathway.

Estrogen receptor (ER)-negative breast cancer cells are probably more aggressive with larger metastatic potential than ER-positive cells. Loss of ER in recurrent breast cancer is associated with poor response to endocrine therapy. G protein-coupled receptor 30 (GPR30) is expressed in half of ER-negative breast cancers. Tumor cell-derived heregulin-ß1 (HRG-ß1) is also found mainly in ER-negative cancer. In SkBr3 breast cancer cells that lack ER but express GPR30, HRG-ß1 upregulates mRNA and protein levels of GPR30 by promoting ErbB2-ErbB3 heterodimerization and activating the downstream MAPK-ERK signaling pathway. Moreover, GPR30 boosts HRG-ß1-induced migration and invasion of SkBr3 cells after combinative treatment with E2, 4-hydroxy-tamoxifen or the specific GPR30 agonist G-1, which are blocked by the specific GPR30 antagonist G-15 or the transfection with the small interfering RNA for GPR30. The ErbB2 inhibitor AG825 and the MEK1/2 inhibitor U0126 also partly inhibit the enhanced migration and invasion. Therefore, HRG-ß1-induced migration and invasion partly depend on the upregulation of GPR30 expression through activation of the ErbB2-ERK pathway in SkBr3 cells. The results of this study indicate that the crosstalk between GPR30 and HRGs signaling is important for endocrine therapy resistance and may provide a new therapeutic way to treat breast cancer.

Acetylsalicylic acid regulates overexpressed small GTPase RhoA in vascular smooth muscle cells through prevention of new synthesis and enhancement of protein degradation.

RhoA has been shown to play a major role in vascular processes and acetylsalicylic acid (aspirin) is known to exert a cytoprotective effect via multiple mechanisms. In the present study, we aimed at investigating the effect of aspirin on RhoA expression under a stress state in rat VSMCs (vascular smooth muscle cells) and the underlying mechanisms. The expression of iNOS (inducible nitric oxide synthase) and iNOS activity as well as NO concentration was significantly promoted by LPS (lipopolysaccharide) accompanying the elevation of RhoA expression, which was blocked by the addition of the iNOS inhibitor L-NIL [L-N6-(1-iminoethyl)lysine dihydrochloride]. Aspirin (30 µM) significantly attenuated the elevation of RhoA, while indomethacin and salicylate had no similar effect. The sGC (soluble guanylate cyclase) inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one) showed the same effect as aspirin in down-regulating RhoA but was reversed by the addition of the cGMP analogue 8-Br-PET-cGMP (ß-phenyl-1,N2-ethano-8-bromoguanosine 3',5'-cyclic monophosphorothioate). 8-Br-PET-cGMP solely enhanced the RhoA expression that was abrogated by preincubation with aspirin. Degradation analysis indicated that aspirin enhanced the protein degradation rate of RhoA and GDP-bound RhoA seemed to be more susceptible to aspirin-enhanced degradation compared with the GTP-bound form. Our results indicate that aspirin attenuates the LPS-induced overexpression of RhoA both by inhibiting new synthesis and accelerating protein degradation, which may help elucidate the multiple beneficial effects of aspirin.

[Optimization of enzymolysis extraction of total anthraquinones from wild rhubarb (Rheum palmatum) via response surface methodology].

OBJECTIVE: To optimize the technology of enzymolysis extraction of total anthraquinones. METHODS: Used the total anthraquinone concentration extracted from rhubarb (Rheum palmatum, L) via enzymolysis as experimental assess index, effect of enzyme dose, enzyme solution temperature, enzyme solution time and pH on total anthraquinone extraction were investigated respectively based on single factor variance analysis. Furthermore, its extraction process was optimized based on response surface methodology. RESULTS: The yield of total anthraquinones demonstrated the top (3.1730 +/- 0.1023 mg/L) while the enzyme dose was up to 0.12 g, besides, for the enzyme solution time, the total anthraquinones yield exhibited a trend of increase with the increase of enzyme solution time and the top concentration of total anthraquinones was up to 2.1410 +/- 0.1252 mg/L while it was 48 h; Moreover, the top field of total anthraquinones were up to 2.2777 +/- 0.2133 mg/L and 4.1360 +/- 0.3877 mg/L while the pH and enzyme solution temperature were up to 4.8 and 50 degrees C in respectively. Finally, the most optimum enzymolysis extraction processing technology via response surface methodology was as follows: pH: 4.59, enzyme dose: 0.1 g as well as enzyme solution temperature: 45.86 degrees C. CONCLUSION: The condition of extraction processing technology is easily-controlled, simple and lower cost, and the final extraction concentration of total anthraquinone is up to 4.3231 mg/L under the processing technology above.

Synthesis of novel azaspiro[3.4]octanes as multifunctional modules in drug discovery.

Step-economic and scalable syntheses of novel thia-azaspiro[3.4]octanes are reported. These spirocycles and some related intermediates can serve as uncharted multifunctional modules for drug discovery chemistry.

[Protective effects of La (NO3)3 on ryegrass seedlings photosynthetic apparatus under NaHCO3 stress].

This paper studied the effects of foliar spraying different concentration La(NO3)3 on the photosynthesis, chlorophyll fluorescence parameters, Mehler reaction, and xanthophyll cycle of ryegrass seedlings under the stress of 150 mmol NaHCO3 x L(-1). Foliar spraying low concentration (0.05 mmol x L(-1)) La (NO3)3 could significantly decrease the decrement of net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and stomatal limited value (Ls) and the increment of intercellular CO2 concentration (Ci) under NaHCO3 stress, efficiently alleviate the inhibitory effects of NaHCO3 stress on PS II photochemical quenching (q(p)), actual photochemical efficiency (phi(PS II)), photosynthetic carbon assimilation- dependent electron transport rate (ETRp), and Mehler reaction- dependent electron transport rate (ETRm), enhance the activities of superoxide dismutase, peroxidase, and ascorbate peroxidase, the non-photochemical energy dissipation (NPQ), the xanthophyll cycle pool (V+A+Z), and the de-epoxidation extent of xanthophyll cycle (A+Z)/(V+A+Z), and thereby, alleviate the damage of photosynthetic apparatus caused by NaHCO3 stress. However, treating with high concentration (0.5 mmol x L(-1)) La(NO3)3 had no obvious alleviation effects. It was suggested that foliar spraying an appropriate concentration La (NO3)3 could not only alleviate the decrease of ryegrass seedling' s photosynthetic rate induced by nonstomata factors and the inhibition of photochemical efficiency, but also accelerate the Mehler reaction under NaHCO3 stress. With the accelerated Mehler reaction, excessive excitation energy could directly be consumed, and the xanthophyll cycle-dependent thermal dissipation could be promoted to efficiently protect the photosynthetic apparatus against photo-damage under NaHCO3 stress. Also, the active oxygen produced by the accelerated Mehler reaction could be scavenged by the enhanced anti-oxidative enzyme activities.

Cytoprotective effects of human interleukin-10 gene transfer against necrosis and apoptosis induced by hepatic cold ischemia/reperfusion injury.

BACKGROUND: Apoptosis as well as necrosis may play an important role in hepatic ischemia/reperfusion (I/R) injury. Interleukin 10 (IL-10), a Th2 type cytokine, modulates inflammatory responses by inhibiting the production of proinflammatory cytokines. The study focused on cytoprotective and antiapoptotic pathways to assess mechanisms by which gene transduction of human IL-10 (hIL-10) may renders grafts resistant to the cold I/R injury. MATERIALS AND METHODS: Adenoviruses encoding hIL-10 or beta-galactosidase (LacZ) were injected via the superior mesenteric vein into prospective donor animals. The donor liver was harvested 48h after transduction, and stored for 12h at 4 degrees C lactated Ringer's solution prior to being transplanted. Graft survival, liver function, the degree of necrosis and apoptosis, and the molecules of apoptotic networks were assessed. RESULTS: Ad-hIL-10 pretreatment significantly prolonged the survival of liver grafts by improving liver function, preserving hepatocyte integrity and architecture, and depressing intrahepatic apoptosis and necrosis. In addition, Ad-hIL-10 pretreatment diminished the release of cytochrome c from mitochondria into cytoplasm and caspase-3 activity, with simultaneous up-regulated of antioxidant HO-1 and anti-antiapoptotic Bcl-2 molecules. CONCLUSION: Adenoviral gene transfer of hIL-10 ameliorated cold I/R injury by decreasing hepatic necrosis and apoptosis. The underlying mechanism of cytoprotective effects may at least be involved with the inhibition of caspase-3 activity and mitochondrial cytochrome c release, and the up-regulation of antiapoptotic (Bcl-2) and antioxidant (HO-1) molecules.

Chapter 19. In vitro studies of phenol coupling enzymes involved in vancomycin biosynthesis.

Oxidative phenol cross-linking reactions play a key role in the biosynthesis of glycopeptide antibiotics such as vancomycin. The vancomycin aglycone contains three cross-links between aromatic amino acid side-chains, which stabilize the folded backbone conformation required for binding to the target D-Ala-D-Ala dipeptide. At least the first cross-link is introduced into a peptide precursor whilst it is still bound as a thioester to a peptide carrier protein (PCP) domain (also called a thiolation domain) within the nonribosomal peptide synthetase. We described here methods for the solid-phase synthesis of peptides and their coupling to PCP domains, which may be useful for in vitro studies of cross-linking and related tailoring reactions during nonribosomal glycopeptide antibiotic biosynthesis.

New insights into the first oxidative phenol coupling reaction during vancomycin biosynthesis.

OxyB catalyzes the first oxidative phenol coupling reaction in vancomycin biosynthesis. OxyB is a P450 hemoprotein whose activity is strictly dependent upon the presence of molecular oxygen. Here, it was shown that label from (18)O(2) is not incorporated into the monocyclic product during catalysis by OxyB. In addition, it was shown that OxyB can convert a model hexapeptide substrate containing (R)-Tyr6, instead of (S)-Tyr6, covalently linked as a C-terminal thioester to a peptidyl carrier protein (PCP-7S) derived from the vancomycin non-ribosomal peptide synthetase (NRPS), into the corresponding epimeric monocyclic product. The binding of this epimeric hexapeptide-PCP conjugate to the Fe(III) form of OxyB, as monitored by UV-vis spectroscopy, revealed a K(d)=35+/-5 microM. Thus, the enzyme reveals a surprising lack of stereospecificity in the binding and transformation of these epimeric substrates.

Antibodies elicited by a virosomally formulated Plasmodium falciparum serine repeat antigen-5 derived peptide detect the processed 47 kDa fragment both in sporozoites and merozoites.

Serine repeat antigen-5 (SERA5) is a candidate antigen for inclusion into a malaria subunit vaccine. During merozoite release and reinvasion the 120 kDa SERA5 precursor protein (P120) is processed, and a complex consisting of an N-terminal 47 kDa (P47) and a C-terminal 18kDa (P18) processing product associates with the surface of merozoites. This complex is thought to be involved in merozoite invasion of and/or egress from host erythrocytes. Here we describe the synthesis and immunogenic properties of virosomally formulated synthetic phosphatidylethanolamine (PE)-peptide conjugates, incorporating amino acid sequence stretches from the N-terminus of Plasmodium falciparum SERA5. Choosing an appropriate sequence was crucial for the development of a peptide that elicited high titers of parasite cross-reactive antibodies in mice. Monoclonal antibodies (mAbs) raised against the optimized peptide FB-23 incorporating amino acids 57-94 of SERA5 bound to both P120 and to P47. Western blotting analysis proved for the first time the presence of SERA5 P47 in sporozoites. In immunofluorescence assays, the mAbs stained SERA5 in all its predicted localizations. The virosomal formulation of peptide FB-23 is suitable for use in humans and represents a candidate component for a multi-valent malaria subunit vaccine targeting both sporozoites and blood stage parasites.

Protective effect of O6-methylguanine-DNA-methyltransferase on mammalian cells.

BACKGROUND: O(6)-methylguanine-DNA-methyltransferase (MGMT) is a specific DNA revising enzyme transferring alkylated groups from DNA to its cysteine residue to avoid the abnormal twisting of DNA. Therefore, it is one of the drug resistant genes targeted in the treatment of cancer. This study explored the protective effect of MGMT gene transferred into mammalian cells. METHODS: Mammalian expression vector containing the MGMT gene cloned from human hepatocytes by RT-PCR was constructed and transferred into K562 cells and human peripheral blood mononuclear cells (PBMCs) via liposome, then assayed for gene expression at RNA and protein levels. MTT assay was used to check the drug resistance of cells transfected with MGMT gene. RESULTS: MGMT gene was successfully cloned. Real-time PCR showed that the mRNA expression in gene transfected groups in K562 cell line and PBMC were 13.4 and 4.0 times that of the empty vector transfected groups respectively. RESULTS: of Western blotting showed distinct higher expression of MGMT in gene transfected group than in other two groups. The IC(50) values increased to 7 and 2 times that of the original values respectively in stable transfected K562 cells and transient transfected PBMC. CONCLUSION: The alkylating resistance of eukaryotic cells is enhanced after being transfected with MGMT gene which protein product performs the protective function, and may provide the reference for the protective model of peripheral blood cells in cancer chemotherapy.

Oxidative phenol coupling reactions catalyzed by OxyB: a cytochrome P450 from the vancomycin producing organism. implications for vancomycin biosynthesis.

OxyB is a cytochrome P450 enzyme that catalyzes the first phenol coupling reaction during the biosynthesis of vancomycin-like glycopeptide antibiotics. The phenol coupling reaction occurs on a linear peptide intermediate linked as a C-terminal thioester to a peptide carrier protein (PCP) domain within the multidomain glycopeptide nonribosomal peptide synthetase (NRPS). Using model peptides with the sequence (R)(NMe)Leu-(R)Tyr-(S)Asn-(R)Hpg-(R)Hpg-(S)Tyr-S-PCP and (R)(NMe)Leu-(R)Tyr-(S)Asn-(R)Hpg-(R)Hpg-(S)Tyr-(S)Dpg-S-PCP (where Hpg = 4-hydroxyphenylglycine, and Dpg = 3,5-dihydroxyphenylglycine), or containing (R)Leu instead of (R)(NMe)Leu, attached to recombinant PCPs derived from modules-6 and -7 in the vancomycin NRPS, we show that cross-linking of Hpg4 and Tyr6 by OxyB can occur in both hexapeptide- and heptapeptide-PCP conjugates. Thus, whereas OxyB may act preferentially on a hexapeptide still linked to the PCP-6 in NRPS subunit-2, it is possible that a linear heptapeptide intermediate linked to PCP-7 in NRPS subunit-3 may also be transformed into monocyclic product. For turnover, OxyB requires electrons, which in vitro can be supplied by spinach ferredoxin and E. coli flavodoxin reductase. Turnover is also dependent upon the presence of molecular oxygen. The model substrate (R)(NMe)Leu-(R)Tyr-(S)Asn-(R)Hpg-(R)Hpg-(S)Tyr-S-PCP is transformed into cross-linked product by OxyB with a kcat of 0.1 s-1 and Km in the range 4-13 muM. Equilibrium binding of this substrate to OxyB, monitored by UV-vis, is accompanied by a typical low-to-high spin state change in the heme, characterized with a Kd of 17 +/- 5 muM.