Agar plate-based activity assay for easy and fast screening of recombinant Pichia pastoris expressing unspecific peroxygenases

Unspecific peroxygenases (UPOs) are promising biocatalysts that catalyze oxyfunctionalization reactions without the need for costly cofactors. Pichia pastoris (reclassified as Komagataella phaffii) is considered an attractive host for heterologous expression of UPOs. However, integration of UPO-expression cassettes into the genome via a single cross-over yields recombinant Pichia transformants with different UPO gene copy numbers resulting in different expression levels. Selection of the most productive Pichia transformants by a commonly used screening in liquid medium in 96-well plates is laborious and lasts up to 5 days. In this work, we developed a simple two-step agar plate-based assay to screen P. pastoris transformants for UPO activity with less effort, within shorter time, and without automated screening devices. After cell growth and protein expression on agar plates supplemented with methanol and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), an additional top agar layer supplemented with ABTS and peroxide is added. UPO activity is visualized within 15 min by formation of green zones around UPO-secreting P. pastoris transformants. The assay was validated with two UPOs, AbrUPO from Aspergillus brasiliensis and evolved PaDa-I from Agrocybe aegerita. The assay results were confirmed in a quantitative 96-deep well plate screening in liquid medium.

Photoelectron Spectroscopy of Oppositely Charged Molecular Switches in the Aqueous Phase: Theory and Experiment

XUV photoelectron spectroscopy (XPS) is a powerful method for investigating the electronic structures of molecules. However, the correct interpretation of results in the condensed phase requires theoretical models that account for solvation. Here we present experimental aqueous-phase XPS of two organic biomimetic molecular switches, NAIP and p-HDIOP. These switches are structurally similar, but have opposite charges and thus present a stringent benchmark for solvation models which need to reproduce the observed ΔeBE = 1.1 eV difference in electron binding energy compared to the 8 eV difference predicted in the gas phase. We present calculations using implicit and explicit solvent models. The latter employs the average solvent electrostatic configuration and free energy gradient (ASEC-FEG) approach. Both nonequilibrium polarizable continuum models and ASEC-FEG calculations give vertical binding energies in good agreement with the experiment for three different computational protocols. Counterions, explicitly accounted for in ASEC-FEG, contribute to the stabilization of molecular states and reduction of ΔeBE upon solvation.

Femtosecond time-resolved photoelectron spectroscopy of the benzyl radical

We present a joint experimental and computational study of the nonradiative deactivation of the benzyl radical, C₇H₇, after UV excitation. Femtosecond time-resolved photoelectron imaging was applied to investigate the photodynamics of the radical. The experiments were accompanied by excited state dynamics simulations using surface hopping. Benzyl has been excited at 265 nm into the D-band (ππ*) and the dynamics was probed using probe wavelengths of 398 nm or 798 nm. At a probe wavelength of 398 nm a single time constant of around 70-80 fs was observed. When the dynamics was probed at 798 nm, a second time constant τ₂ = 1.5 ps was visible, which can be attributed to further non-radiative deactivation to the lower-lying D₁/D₂ states.

Communication: On the first ionization threshold of the C2H radical

The slow photoelectron spectrum of the ethynyl radical has been recorded for the first time by using the DESIRS beamline of the SOLEIL synchrotron facility. Ethynyl was generated using a microwave discharge flow tube. The observation of the X⁺Π3←XΣ+2 transition allowed the first direct measurement of the adiabatic ionization threshold of this radical (E_I = 11.641(5) eV). The experimental results are supported by ab initio calculations. Our preliminary investigation of the cationic ground state potential energy surfaces predicts a non-negligible Renner-Teller effect which has not been discussed previously.

Characterization of the chemical bonding in inner layers of composite materials

The efficiency of near edge structure investigations in electron energy loss spectroscopy (EELS) is discussed for characterizing the chemical bonding of elements present in the interfacial zone in fibre/matrix composites at nanometre resolution. Two different examples of corresponding analyses are given for a SiC-fibre reinforced borosilicate glass. In particular, the chemical bonding between silicon and carbon or oxygen (e.g. SiC, SiO(2) and SiO(x)C(y)), respectively, is characterized. The results have been attained in a fingerprint manner by comparing the fine structure measured from a material of unknown stoichiometry to that of a standard specimen. In addition, a possibility is demonstrated to image the chemical bonding by energy-filtered microscopy using energy loss near edge structures (ELNES).

Ulcerative colitis specific cytotoxic IgG-autoantibodies against colonic epithelial cancer cells

Serum antibodies cytotoxic to the colon cancer cell line RPMI 4788 were studied in 42 patients with ulcerative colitis, 61 patients with Crohn's disease, 27 patients with other inflammatory diseases (disease-controls) and 22 healthy controls. Cytotoxicity of antibodies towards RPMI 4788 was studied by means of a chromium release assay using peripheral blood mononuclear leucocytes of healthy subjects as effector cells. Using a four hour antibody dependent cell mediated cytotoxicity assay sera from 29% of ulcerative colitis patients contained antibodies cytotoxic for the target, while only 3% of the Crohn's patients and 6% of the disease controls and non of the healthy controls were positive. When an 18 hour assay was applied, however, not only 40% of ulcerative colitis patients, but also 14% of Crohn's patients and 21% of disease controls were found positive. The reactive antibody in the four hour assay was mainly of the IgG class, which points at a classical antibody dependent cell mediated cytotoxicity mechanism. In the 18 hour cytotoxic assay IgG and particularly IgM antibodies were found to be reactive. This suggests that in the latter case other cellular cytotoxic mechanism might be involved. There was a significant inverse correlation between the appearance of the ulcerative colitis restricted IgG-anticolon epithelial cell antibodies (four hour assay) and the disease activity (p less than 0.01). Absorption studies showed that the reactive antigen is not specific for ulcerative colitis colonic tissue, but is similarly found in Crohn's bowel tissue, and to a lower extent in normal bowel, liver and kidney. The reactive antigen, however, could not be detected in brain and lymphoblastoid cells.

[Intestinal spontaneous cell-mediated cytotoxicity and its immunoregulation in patients with chronic inflammatory bowel disease and controls]

Isolated intestinal mononuclear cells (IMNL) exhibit spontaneous cell-mediated cytotoxicity (SCMC) in one third of the cases. IMNL suppress the SCMC of peripheral blood lymphocytes. The suppression by IMNL of patients with chronic inflammatory bowel disease is diminished.

Immune status in Crohn's disease. VI. Immunoregulation evaluated by multiple, distinct T-suppressor cell assays of lymphocyte proliferation, and by enumeration of immunoregulatory T-lymphocyte subsets

In 28 patients with Crohn's disease, 6 patients with ulcerative colitis, and 34 healthy controls, immunoregulatory function of peripheral blood mononuclear cells was investigated by evaluating the suppression of lymphocyte proliferative responses to mitogens (phytohemagglutinin, concanavalin A, pokeweed mitogen) and to allogeneic lymphocytes (mixed lymphocyte culture) using simultaneously five functional assays as follows: (a) spontaneous T-suppressor-cell activity, (b) concanavalin A-generated T-suppressor-cell activity, both with (3000 rads) and without irradiation of suppressor cells, and (c) allogeneic mixed lymphocyte culture-generated T-suppressor-cell activity, again both with and without irradiation. Concanavalin A- and mixed lymphocyte culture-generated T-suppressor-cell activities were evaluated both in the autologous and the allogeneic system. In addition, using monoclonal antibodies, we determined proportions of T-helper and T-suppressor/cytotoxic lymphocytes. Inactive patients did not differ from normal either in the proportions of immunoregulatory lymphocytes or in the suppression of the various lymphocyte proliferative responses in any of the five T-suppressor-cell assays evaluated. In patients with active disease, however, an impairment of suppression of phytohemagglutinin-, pokeweed mitogen-, and mixed lymphocyte culture-stimulated proliferation of autologous lymphocytes was observed in the concanavalin A-generated, irradiated suppressor assay. In the spontaneous suppressor assay, suppression of phytohemagglutinin- and concanavalin A-stimulated lymphocyte proliferation was significantly lower in active disease than in remission. Thus, in peripheral blood of patients with Crohn's disease who are in remission, there is no indication for an immunoregulatory defect in any of the evaluated assay systems. Single selective, moderate defects in suppression of proliferation of various lymphocyte subpopulations are restricted to active disease.

[Serodiagnosis of Crohn's disease]

Three serological tests, recommended as being of diagnostic value for Crohn's disease, were evaluated in 39 patients with Crohn's disease and--as controls--in 27 patients with ulcerative colitis, 45 healthy persons and 65 patients with inflammatory diseases other than Crohn's disease or ulcerative colitis. The tests were the determination of (1) serum antibodies to pseudomonas-like organisms (PLO) by means of indirect immunofluorescence; (2) agglutinating serum antibodies to 4 strains of anaerobic gram-positive coccoid rods (species of Eubacterium, Peptostreptococcus and Coprococcus); and (3) serum antibodies to perinuclear antigens in buccal mucosa of Crohn's disease patients by immunofluorescence. The results indicate that the occurrence of high-titer antibodies to PLO is reasonably sensitive for Crohn's disease, but has a low specificity, and that antibodies to perinuclear antigens in buccal mucosa have both low sensitivity and specificity. However, the occurrence of agglutinins to 4 strains of anaerobic grampositive coccoid rods is significantly higher in Crohn's disease than in ulcerative colitis, patients with other diseases and healthy controls. Thus the determination of these agglutinins does not discriminate between Crohn's disease and ulcerative colitis; but it is a serodiagnostic adjunct in the diagnosis of chronic inflammatory bowel diseases.

Selected bacterial antibodies in Crohn's disease and ulcerative colitis

Agglutinins to four strains of anaerobic gram-positive coccoid rods (species of Eubacterium, Peptostreptococcus and Coprococcus) were found in significantly higher frequency in Crohn's disease (CD) than in ulcerative colitis (UC) and in other diseased control subjects and were virtually absent in apparently healthy subjects. When the posterior probability of having CD was calculated on the basis of these agglutination reactions, 64% of patients with CD and 34% of patients with UC but only 10% of diseased controls and none of the healthy controls were regarded as 'probable' or 'definite' cases of CD. However, the posterior probability of CD did not sharply differentiate between CD and UC but indicated chronic inflammatory bowel disease. Factors contributing to the appearance of these agglutinins in CD were also evaluated. The findings would indicate the importance of a damaged intestinal mucosal barrier for the production of these agglutinins, provided the antigens are present in the intestine. No significant differences were observed between the occurrence of antibodies to pseudomonas-like organisms (PLO) in CD and the various control groups. The study could not add further evidence to the hypothesis of a possible aetiopathogenic role of PLO in CD.

[Interactions between nuclear polyhedrosis viruses and vertebrate cells (author's transl)]

The influence of NPV on mammals was tested in animals and tissue cultures. Toxicity experiments were performed in rats: per os application (3 X 10(9) Virusinclusionbodies per kg body weight) and intravenous (5 X 10(8) Virusinclusionbodies per kg body weight). Skin irrition was performed in guinea pigs. In each tested animal no virus induced changes could be shown. Tissue culture studies were done in tissues of human (Hela Ohio), monkey (Vero) and rats (REC). The infectious unit was Ac NPV derived from infected, virus-producing insect tissue cultures. Three blind passages were done in each examined cell type and no signs of viral replication could be shown. An additional infectivity assay of cellfree extracts in insect cell cultures as indicator system remained negative.

Virus-specific proteins associated with the replication complex of poliovirus RNA

The poliovirus replication complex was isolated and purified from infected HeLa S3 cells. Preparations with RNA-dependent RNA polymerase activity were concentrated 200- and 1000-fold with respect to the original virus and total protein content. The enzyme activity was found to be associated with the proteins NCVPI, 2, 3, 4, (5), 6 and VPl/NCVPx. The structural proteins VP2, 3 and 4 were not present. Addition of cycloheximide to infected cells resulted in a decrease in the in vitro polymerase activity and a loss in NCVPI content. Treatment of the infected cells with toloylsulphonyl-phenylalanine chloromethyl ketone (TPCK) and iodoacetamide (IAA) led to an inhibition of in vivo RNA synthesis. The 750 g supernatant fluids obtained from extracts of these cells were able to block RNA synthesis in vitro. Electrophoretic profiles of the respective protein compositions indicate that large virus precursor proteins are responsible for the inhibition of poliovirus RNA synthesis in vivo and in vitro.

Reversible inhibition of poliovirus RNA synthesis in vivo and in vitro by viral products

In poliovirus-infected HeLa-S3 cells, the protease inhibitors tolylsulfonyl-phenylalanyl chloromethyl ketone and iodoacetamide cause an accumulation of large precursor proteins, and they block viral RNA synthesis most probably via these products. Viral RNA polymerase activity can, however, be extracted by detergent containing buffer (Tris/Nonidet P-40, deoxycholate) from the inhibited cells. Only cytoplasmic extracts from infected cells treated with tolylsulfonyl-phenylalanyl chloromethyl ketone or iodoacetamide contain a protein which inhibits the in vitro polymerase reaction.