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Effects of post-translational modifications catalysed by pollen transglutaminase on the functional properties of microtubules and actin filaments
TGases (transglutaminases) are a class of calcium-dependent enzymes that catalyse the interactions between acyl acceptor glutamyl residues and amine donors, potentially making crosslinks between proteins. To assess the activity of apple (Malus domestica) pollen TGase on the functional properties of actin and tubulin, TGase was prepared from apple pollen by hydrophobic interaction chromatography and assayed on actin and tubulin purified from the same cell type. The enzyme catalysed the incorporation of putrescine in the cytoskeleton monomers. When tested on actin filaments, pollen TGase induced the formation of high-molecular-mass aggregates of actin. Use of fluorescein– cadaverine showed that the labelled polyamine was incorporated into actin by pollen TGase, similar to with guinea pig liver TGase. The pollen TGase also reduced the enzyme activity and the binding of myosin to TGase-treated actin filaments. Polymerization of tubulin in the presence of pollen TGase also yielded the formation of high molecular mass aggregates. Furthermore, the pollen TGase also affected the binding of kinesin to microtubules and reduced the motility of microtubules along kinesincoated slides. These results indicate that the pollen tube TGase can control different properties of the pollen tube cytoskeleton (including the ability of actin and tubulin to assemble and their interaction with motor proteins) and consequently regulate the development of pollen tubes
An extracellular transglutaminase is required for apple pollen tube growth
An extracellular form of the calcium-dependent protein-crosslinking enzyme TGase (transglutaminase) was demonstrated to be involved in the apical growth of Malus domestica pollen tube. Apple pollen TGase and its substrates were co-localized within aggregates on the pollen tube surface, as determined by indirect immunofluorescence staining and the in situ cross-linking of fluorescently labelled substrates. TGase-specific inhibitors and an anti-TGase monoclonal antibody blocked pollen tube growth, whereas incorporation of a recombinant fluorescent mammalian TGase substrate (histidine-tagged green fluorescent protein:His6– Xpr–GFP) into the growing tube wall enhanced tube length and germination, consistent with a role of TGase as a modulator of cell wall building and strengthening. The secreted pollen TGase catalysed the cross-linking of both PAs (polyamines) into proteins (released by the pollen tube) and His6-Xpr-GFP into endogenous or exogenously added substrates. A similar distribution of TGase activitywas observed in planta on pollen tubes germinating inside the style, consistent with a possible additional role for TGase in the interaction between the pollen tube and the style during fertilization
Frequency Selection to Improve the Performance of Microwave Breast Cancer Detecting Support Vector Model by Using Genetic Algorithm
This paper presents an innovative paradigm for breast cancer detection by leveraging a Support Vector Machine (SVM) based model fueled with numerical data obtained from the cutting-edge MammoWave device. Operating in the microwave spectrum between 1 to 9 GHz and boasting a 5 MHz sampling rate, MammoWave emerges as a groundbreaking solution, specifically addressing the limitations posed by conventional methods, particularly for women under 50. This technological advancement opens a promising avenue for more frequent and precise breast health monitoring. To enhance the efficacy of the SVM model, our research introduces a metaheuristic-based methodology, strategically navigating the selection of frequencies crucial for breast cancer detection within the MammoWave dataset. Overcoming the challenge of judicious frequency selection, our approach employs wrapper methods in metaheuristic algorithms. These algorithms iterate through subsets of frequencies, guided by the SVM model's performance, culminating in the identification of the optimal frequency subset that significantly refines precision in breast cancer detection. Moreover, a novel cost function is proposed to strike a balanced trade-off between sensitivity and specificity, ensuring an acceptable accuracy rate. The results exhibit a noteworthy 10% increase in specificity, a milestone achievement for the MammoWave device, yielding an overall detection rate of approximately 62%. This research underscores the potential of seamlessly integrating metaheuristic algorithms into frequency selection, thereby contributing significantly to the ongoing refinement of MammoWave's capabilities in breast cancer detection
Far Ultraviolet Spectra of B Stars near the Ecliptic
Spectra of B stars in the wavelength range of 911-1100 A have been obtained
with the EURD spectrograph onboard the Spanish satellite MINISAT-01 with ~5 A
spectral resolution. IUE spectra of the same stars have been used to normalize
Kurucz models to the distance, reddening and spectral type of the corresponding
star. The comparison of 8 main-sequence stars studied in detail (alpha Vir,
epsilon Tau, lambda Tau, tau Tau, alpha Leo, zeta Lib, theta Oph, and sigma
Sgr) shows agreement with Kurucz models, but observed fluxes are 10-40% higher
than the models in most cases. The difference in flux between observations and
models is higher in the wavelength range between Lyman alpha and Lyman beta. We
suggest that Kurucz models underestimate the FUV flux of main-sequence B stars
between these two Lyman lines. Computation of flux distributions of
line-blanketed model atmospheres including non-LTE effects suggests that this
flux underestimate could be due to departures from LTE, although other causes
cannot be ruled out. We found the common assumption of solar metallicity for
young disk stars should be made with care, since small deviations can have a
significant impact on FUV model fluxes. Two peculiar stars (rho Leo and epsilon
Aqr), and two emission line stars (epsilon Cap and pi Aqr) were also studied.
Of these, only epsilon Aqr has a flux in agreement with the models. The rest
have strong variability in the IUE range and/or uncertain reddening, which
makes the comparison with models difficult.Comment: 25 pages, 6 figures, to be published in The Astrophysical Journa
Protein-Glutamine Gamma-Glutamyltransferase
info:eu-repo/semantics/publishedVersio
A possible architecture of the planetary system HR 8799
HR8799 is a nearby A-type star with a debris disk and three planetary
candidates recently imaged directly. We undertake a coherent analysis of
various portions of observational data on all known components of the system.
The goal is to elucidate the architecture and evolutionary status of the
system. We try to further constrain the age and orientation of the system,
orbits and masses of the companions, as well as the location of dust. From the
high luminosity of debris dust and dynamical constraints, we argue for a rather
young system's age of <50Myr. The system must be seen nearly, but not exactly,
pole-on. Our analysis of the stellar rotational velocity yields an inclination
of 13-30deg, whereas i>20deg is needed for the system to be dynamically stable,
which suggests a probable inclination range of 20-30deg. The spectral energy
distribution is naturally reproduced with two dust rings associated with two
planetesimal belts. The inner "asteroid belt" is located at ~10AU inside the
orbit of the innermost companion and a "Kuiper belt" at >100AU is just exterior
to the orbit of the outermost companion. The dust masses in the inner and outer
ring are estimated to be ~1E-05 and 4E-02 M_earth, respectively. We show that
all three planetary candidates may be stable in the mass range suggested in the
discovery paper by Marois et al. 2008 (between 5 and 13 Jupiter masses), but
only for some of all possible orientations. Stable orbits imply a double
(4:2:1) mean-motion resonance between all three companions. We finally show
that in the cases where the companions themselves are orbitally stable, the
dust-producing planetesimal belts are also stable against planetary
perturbations.Comment: 12 pages, 14 figures, 4 tables, accepted to be published in Astronomy
& Astrophysics (May 20, 2009
The Penn State-Torun Centre for Astronomy Planet Search stars. I. Spectroscopic analysis of 348 red giants
We present basic atmospheric parameters (Teff, logg, vt and [Fe/H]) as well
as luminosities, masses, radii and absolute radial velocities for 348 stars,
presumably giants, from the ~1000 star sample observed within the Penn
State-Torun Centre for Astronomy Planet Search with the High Resolution
Spectrograph of the 9.2m Hobby-Eberly Telescope. The stellar parameters are key
ingredients in proper interpretation of newly discovered low-mass companions
while a systematic study of the complete sample will create a basis for future
statistical considerations concerning low-mass companions appearance around
evolved low and intermediate-mass stars. The atmospheric parameters were
derived using a strictly spectroscopic method based on the LTE analysis of
equivalent widths of FeI and FeII lines. With existing photometric data and the
Hipparcos parallaxes we estimated stellar masses and ages via evolutionary
tracks fitting. The stellar radii were calculated from either estimated masses
and the spectroscopic logg or from the spectroscopic Teff and estimated
luminosities. The absolute radial velocities were obtained by cross-correlating
spectra with a numerical template. We completed the spectroscopic analysis for
332 stars of which 327 were found to be giants. For the remaining 16 stars with
incomplete data a simplified analysis was applied. The results show that our
sample is composed of stars with Teff = 4055-6239 K, logg = 1.39-4.78 (5 dwarfs
were identified), logL/Lo = -1.0-3, M = 0.6-3.4 Mo, R = 0.6-52 Ro. The stars in
our sample are generally less metal abundant than the Sun with median [Fe/H] =
-0.15. The estimated uncertainties in the atmospheric parameters were found to
be comparable to those reached in other studies. However, due to lack of
precise parallaxes the stellar luminosities and, in turn, the masses are far
less precise, within 0.2 Mo in best cases, and 0.3 Mo on average.Comment: 31 pages, 19 figures, 10 tables, accepted for publication in A&
CRIRES-POP: A library of high resolution spectra in the near-infrared
New instrumental capabilities and the wealth of astrophysical information
extractable from the near-infrared wavelength region have led to a growing
interest in the field of high resolution spectroscopy at 1-5 mu. We aim to
provide a library of observed high-resolution and high signal-to-noise-ratio
near-infrared spectra of stars of various types throughout the
Hertzsprung-Russell diagram. This is needed for the exploration of spectral
features in this wavelength range and for comparison of reference targets with
observations and models.
High quality spectra were obtained using the CRIRES near-infrared
spectrograph at ESO's VLT covering the range from 0.97 to 5.3 mu at high
spectral resolution. Accurate wavelength calibration and correction for of
telluric lines were performed by fitting synthetic transmission spectra for the
Earth's atmosphere to each spectrum individually. We describe the observational
strategy and the current status and content of the library which includes 13
objects. The first examples of finally reduced spectra are presented. This
publication will serve as a reference paper to introduce the library to the
community and explore the extensive amount of material.Comment: accepted for publication in A&A; see also the project webpage
http://www.univie.ac.at/crirespo
Detection of the 128 day radial velocity variations in the supergiant {\alpha} Persei. Rotational modulations, pulsations, or a planet?
Aims. In order to search for and study the nature of the low-amplitude and
long-periodic radial velocity (RV) variations of massive stars, we have been
carrying out a precise RV survey for supergiants that lie near or inside the
Cepheid instability strip.
Methods. We have obtained high-resolution spectra of {\alpha} Per (F5 Ib)
from November 2005 to September 2011 using the fiber-fed Bohyunsan Observatory
Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO).
Results. Our measurements reveal that {\alpha} Per shows a periodic RV
variation of 128 days and a semi-amplitude of 70 m/s. We find no strong
correlation between RV variations and bisector velocity span (BVS), but the
128-d peak is indeed present in the BVS variations among several other
significant peaks in periodogram.
Conclusions. {\alpha} Per may have an exoplanet, but the combined data
spanning over 20 years seem to suggest that the 128-d RV variations have not
been stable on long-term scale, which is somewhat difficult to reconcile with
the exoplanet explanation. We do not exclude the pulsational nature of the
128-d variations in {\alpha} Per. Although we do not find clear evidence for
surface activity or rotational modulations by spots, coupled with the fact that
the expected rotation period is ~ 130 days the rotational modulation seems to
be the most likely cause of the RV variations. More observational data and
research are needed to clearly determine the origin of RV the variations in
{\alpha} Per.Comment: 7 pages, 10 figures, 4 table
SAM levels, gene expression of SAM synthetase, methionine synthase and ACC oxidase, and ethylene emission from N. suaveolens flowers
S′adenosyl-l-methionine (SAM) is a ubiquitous methyl donor and a precursor in the biosynthesis of ethylene, polyamines, biotin, and nicotianamine in plants. Only limited information is available regarding its synthesis (SAM cycle) and its concentrations in plant tissues. The SAM concentrations in flowers of Nicotiana suaveolens were determined during day/night cycles and found to fluctuate rhythmically between 10 and 50 nmol g−1 fresh weight. Troughs of SAM levels were measured in the evening and night, which corresponds to the time when the major floral scent compound, methyl benzoate, is synthesized by a SAM dependent methyltransferase (NsBSMT) and when this enzyme possesses its highest activity. The SAM synthetase (NsSAMS1) and methionine synthase (NsMS1) are enzymes, among others, which are involved in the synthesis and regeneration of SAM. Respective genes were isolated from a N. suaveolens petal cDNA library. Transcript accumulation patterns of both SAM regenerating enzymes matched perfectly those of the bifunctional NsBSMT; maximum mRNA accumulations of NsMS1 and NsSAMS1 were attained in the evening. Ethylene, which is synthesized from SAM, reached only low levels of 1–2 ppbv in N. suaveolens flowers. It is emitted in a burst at the end of the life span of the flowers, which correlates with the increased expression of the 1-aminocyclopropane-1-carboxylate oxidase (NsACO)
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