51,425 research outputs found
Diferencijacija Pseudomonas i Stenotrophomonas vrsta izolovanih iz riba primenom molekularnih metoda i MALDI-TOF metode
For the purpose of precise antibiotic susceptibility testing it is necessary to clearly distinguish Pseudomonas and Stenotrophomonas genera, considering acquired resistance of Pseudomonas species, as well as the intrinsic resistance of Stenotrophomonas species. This is why in the identification of the 51 isolates originated from fish, the following methods were used: standard PCR, 16S rRNA gene sequencing, and MALDI-TOF. The results of the standard PCR test, 16S rRNA gene sequencing and MALDI-TOF analysis confirmed 35 strains to belong to the Pseudomonas genus. Standard PCR test and VITEK MS device confirmed that 10 strains belong to Stenotrophomonas maltophilia species. Three strains were positive in both standard PCR tests for Pseudomonas and Stenotrpohomonas. 16S rRNA gene sequencing identified these 3 strains to be 99% Pseudomonas sp. and 99% Stenotrophomonas sp. VITEK MS first identified these three strains as 99% Stenotrophomonas, and in the repeated identification it identified them as 99% Pseudomonas. MALDI TOF/TOF 4800 Plus device identified these strains as Stenotrophomonas. Three strains were negative in both standard PCR tests for Pseudomonas and Stenotrpohomonas. 16S rRNA gene sequencing identified these 3 strains to be 99% Pseudomonas sp. and 99% Stenotrophomonas sp. VITEK MS first identified these three strains as 99% Stenotrophomonas, and in the repeated identification it identified them as 99% Pseudomonas. MALDI TOF/TOF 4800 Plus device identified these strains as Stenotrophomonas. Although modern test methods that have very high specificity (PCR, 16S rRNA gene Pseudomonas and Stenotrophomonas species for 6 isolates could not be reached using the above mentioned methods.S obzirom na znaÄaj steÄene rezistencije Pseudomonas vrsta, kao i na intrinziÄnu rezistenciju Stenotrophomonas vrsta, a u cilju preciznog ispitivanja osetljivosti na antibiotike, neophodna je jasna diferencijacija pripadnika ovih rodova bakterija. U tom cilju su u identifikaciji 51 izolata poreklom od riba koriÅ”Äene metode: standardni PCR, 16S rRNA sekvenciranje gena, MALDI-TOF. Rezultati standardnog PCR testa, 16S rRNA sekvenciranja gena i MALDI-TOF analize su za 35 sojeva potvrdili pripadnost rodu Pseudomonas. Standardnim PCR testom i primenom aparata VITEK MS utvrÄeno je da 10 sojeva pripada vrsti Stenotrophomonas maltophilia. U 16S rRNA sekvenciranju gena 3 soja koja su bila pozitivna u oba standardna PCR testa identifikovana su kao 99% Pseudomonas sp. i 99% Stenotrophomonas sp. VITEK MS je ova tri soja u prvoj identifikaciji identifikovao kao 99% Stenotrophomonas, a u ponovljenoj identifikaciji kao 99% Pseudomonas. Ti sojevi su na aparatu MALDI TOF/TOF 4800 Plus bili identifikovani kao Stenotrophomonas. U 16S rRNA sekvenciranju gena tri soja koja su bila negativna u oba standardna PCR testa su identifikovana kao 99% Pseudomonas sp. i 99% Stenotrophomonas sp. Aparat VITEK MS je ova tri soja identifikovao u jednoj identifikaciji kao 99% Stenotrophomonas, a u drugoj identifikaciji 99% kao Pseudomonas. Ti sojevi su na aparatu MALDI TOF/ TOF 4800 Plus bili identifikovani kao Stenotrophomonas. Iako su u ovom istraživanju koriÅ”Äene savremene metode ispitivanja koje imaju vrlo visoku specifiÄnost (PCR, 16s rRNK sequencing, MALDI TOF) precizna diferencijacija Pseudomonas i Stenotrophomonas vrsta nije mogla biti postignuta
Mass Spectrometric Characterization of Oligomers in Pseudomonas aeruginosa Azurin Solutions
We have employed laser-induced liquid bead ion desorption mass spectroscopy (LILBID MS) to study the solution behavior of Pseudomonas aeruginosa azurin as well as two mutants and corresponding Re-labeled derivatives containing a Re(CO)_(3)(4,7-dimethyl-1,10-phenanthroline)^+ chromophore appended to a surface histidine. LILBID spectra show broad oligomer distributions whose particular patterns depend on the solution composition (pure H_(2)O, 20ā30 mM NaCl, 20 and 50 mM NaP_i or NH_(4)P_i at pH = 7). The distribution maximum shifts to smaller oligomers upon decreasing the azurin concentration and increasing the buffer concentration. Oligomerization is less extensive for native azurin than its mutants. The oligomerization propensities of unlabeled and Re-labeled proteins are generally comparable, and only Re126 shows some preference for the dimer that persists even in highly diluted solutions. Peak shifts to higher masses and broadening in 20ā50 mM NaP_i confirm strong azurin association with buffer ions and solvation. We have found that LILBID MS reveals the solution behavior of weakly bound nonspecific protein oligomers, clearly distinguishing individual components of the oligomer distribution. Independently, average data on oligomerization and the dependence on solution composition were obtained by time-resolved anisotropy of the Re-label photoluminescence that confirmed relatively long rotation correlation times, 6ā30 ns, depending on Reāazurin and solution composition. Labeling proteins with Re-chromophores that have long-lived phosphorescence extends the time scale of anisotropy measurements to hundreds of nanoseconds, thereby opening the way for investigations of large oligomers with long rotation times
The HRX-BL Lac sample - evolution of BL Lac objects
The unification of X-ray and radio selected BL Lacs has been an outstanding
problem in the blazar research in the past years. Recent investigations have
shown that the gap between the two classes can be filled with intermediate
objects and that apparently all differences can be explained by mutual shifts
of the peak frequencies of the synchrotron and inverse Compton component of the
emission. We study the consequences of this scheme using a new sample of X-ray
selected BL Lac objects comprising 104 objects with z<0.9 and a mean redshift
z=0.34. 77 BL Lacs, of which the redshift could be determined for 64 (83%)
objects, form a complete sample. The new data could not confirm our earlier
result, drawn from a subsample, that the negative evolution vanishes below a
synchrotron peak frequency log (peak-frequency) = 16.5. The complete sample
shows negative evolution at the 2 sigma level ( = 0.42 +- 0.04). We
conclude that the observed properties of the HRX BL Lac sample show typical
behaviour for X-ray selected BL Lacs. They support an evolutionary model, in
which flat-spectrum radio quasars (FSRQ) with high energetic jets evolve
towards low frequency peaked (mostly radio-selected) BL Lac objects and later
on to high frequency peaked (mostly X-ray selected) BL Lacs.Comment: 24 pages, 35 figures, accepted by A&
Robust limit on a varying proton-to-electron mass ratio from a single H2 system
The variation of the dimensionless fundamental physical constant mu=m_p/m_e
can be checked through observation of Lyman and Werner lines of molecular
hydrogen in the spectra of distant QSOs. Our intention is to asses the accuracy
of the investigation concerning a possible variation of mu and to provide more
robust results for QSO 0347-383. The goal in mind is to resolve the current
controversy on variation of mu and devise explanations for the different
findings. We achieve this not by another single result but by providing
alternative approaches to the problem. An analysis based on independent data
sets of QSO 0347-383 is put forward and new approaches for some of the steps
involved in the data analysis are introduced. We analyse two independent sets
of observations of the same absorption system and for the first time we apply
corrections for the observed offsets between discrete spectra Drawing on two
independent observations of a single absorption system in QSO 0347-383 our
detailed analysis yields dmu/mu = 15 +/- (9_stat + 6_sys) x 10^{-6} at
z_abs=3.025. Based on the overall goodness-of-fit we estimate the limit of
accuracy to about 300 m/s, consisting of roughly 180 m/s due to the uncertainty
of the fit and about 120 m/s allocated to systematics This work presents
alternative approaches to handle systematics and introduces methods required
for precision analysis of QSO spectra available in the near future.Comment: 9 pages, 10 figures, submitted to A&
Iron-based ferritin nanocore as a contrast agent
Self-assembling protein cages have been exploited as templates for nanoparticle synthesis. The ferritin molecule, a protein cage present in most living systems, stores excess soluble ferrous iron in the form of an insoluble ferric complex within its cavity. Magnetic nanocores formed by loading excess iron within an engineered ferritin from Archaeoglobus fulgidus (AfFtn-AA) were studied as a potential magnetic resonance (MR) imaging contrast agent. The self-assembly characteristics of the AfFtn-AA were investigated using dynamic light scattering technique and size exclusion chromatography. Homogeneous size distribution of the assembled nanoparticles was observed using transmission electron microscopy. The magnetic properties of iron-loaded AfFtn-AA were studied using vibrating sample magnetometry. Images obtained from a 3.0 T whole-body MRI scanner showed significant brightening of T1 images and signal loss of T2 images with increased concentrations of iron-loaded AfFtn-AA. The analysis of the MR image intensities showed extremely high R2 values (5300āmM^(ā1)ās^(ā1)) for the iron-loaded AfFtn-AA confirming its potential as a T2 contrast agent
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