65 research outputs found
Engineering of Metabolic Pathways by Artificial Enzyme Channels.
Application of industrial enzymes for production of valuable chemical compounds has greatly benefited from recent developments in Systems and Synthetic Biology. Both, in vivo and in vitro systems have been established, allowing conversion of simple into complex compounds. Metabolic engineering in living cells needs to be balanced which is achieved by controlling gene expression levels, translation, scaffolding, compartmentation, and flux control. In vitro applications are often hampered by limited protein stability/half-life and insufficient rates of substrate conversion. To improve stability and catalytic activity, proteins are post-translationally modified and arranged in artificial metabolic channels. Within the review article, we will first discuss the supramolecular organization of enzymes in living systems and second summarize current and future approaches to design artificial metabolic channels by additive manufacturing for the efficient production of desired products
The helium atom in a strong magnetic field
We investigate the electronic structure of the helium atom in a magnetic
field b etween B=0 and B=100a.u. The atom is treated as a nonrelativistic
system with two interactin g electrons and a fixed nucleus. Scaling laws are
provided connecting the fixed-nucleus Hamiltonia n to the one for the case of
finite nuclear mass. Respecting the symmetries of the electronic Ham iltonian
in the presence of a magnetic field, we represent this Hamiltonian as a matrix
with res pect to a two-particle basis composed of one-particle states of a
Gaussian basis set. The corresponding generalized eigenvalue problem is solved
numerically, providing in the present paper results for vanish ing magnetic
quantum number M=0 and even or odd z-parity, each for both singlet and triplet
spin symmetry. Total electronic energies of the ground state and the first few
excitations in each su bspace as well as their one-electron ionization energies
are presented as a function of the magnetic fie ld, and their behaviour is
discussed. Energy values for electromagnetic transitions within the M=0 sub
space are shown, and a complete table of wavelengths at all the detected
stationary points with respect to their field dependence is given, thereby
providing a basis for a comparison with observed ab sorption spectra of
magnetic white dwarfs.Comment: 21 pages, 4 Figures, acc.f.publ.in J.Phys.
Sex-Biased Expression of MicroRNAs in Schistosoma mansoni
Schistosomiasis is an important neglected tropical disease caused by digenean helminth parasites of the genus Schistosoma. Schistosomes are unusual in that they are dioecious and the adult worms live in the blood system. MicroRNAs play crucial roles during gene regulation and are likely to be important in sex differentiation in dioecious species. Here we characterize 112 microRNAs from adult Schistosoma mansoni individuals, including 84 novel microRNA families, and investigate the expression pattern in different sexes. By deep sequencing, we measured the relative expression levels of conserved and newly identified microRNAs between male and female samples. We observed that 13 microRNAs exhibited sex-biased expression, 10 of which are more abundant in females than in males. Sex chromosomes showed a paucity of female-biased genes, as predicted by theoretical evolutionary models. We propose that the recent emergence of separate sexes in Schistosoma had an effect on the chromosomal distribution and evolution of microRNAs, and that microRNAs are likely to participate in the sex differentiation/maintenance process
Hydrogen Molecules In Superstrong Magnetic Field: II. Excitation Levels
We study the energy levels of H molecules in a superstrong magnetic field
(B\go 10^{12} G), typically found on the surfaces of neutron stars. The
interatomic interaction potentials are calculated by a Hartree-Fock method with
multi-configurations assuming electrons are in the ground Landau state. Both
the aligned configurations and arbitrary orientations of the molecular axis
with respect to the magnetic field axis are considered. Different types of
molecular excitations are then studied: electronic excitations, aligned (along
the magnetic axis) vibrational excitations, transverse vibrational excitations
(a constrained rotation of the molecular axis around the magnetic field line).
Similar results for the molecular ion H are also obtained and compared
with previous variational calculations. Both numerical results and analytical
fitting formulae are given for a wide range of field strengths. In contrast to
the zero-field case, it is found that the transverse vibrational excitation
energies can be larger than the aligned vibration excitation, and they both can
be comparable or larger than the electronic excitations. For B\go
B_{crit}=4.23\times 10^{13} G, the Landau energy of proton is appreciable and
there is some controversy regarding the dissociation energy of H. We show
that H is bound even for and that neither proton has a Landau
excitation in the ground molecular state.Comment: Revtex (45 pages), 3 postscript figures; Phys. Rev. A in pres
Modular assembly of proteins on nanoparticles
Generally, the high diversity of protein properties necessitates the development of unique nanoparticle bio-conjugation methods, optimized for each different protein. Here we describe a universal bio-conjugation approach which makes use of a new recombinant fusion protein combining two distinct domains. The N-terminal part is Glutathione S-Transferase (GST) from Schistosoma japonicum, for which we identify and characterize the remarkable ability to bind gold nanoparticles (GNPs) by forming gold–sulfur bonds (Au–S). The C-terminal part of this multi-domain construct is the SpyCatcher from Streptococcus pyogenes, which provides the ability to capture recombinant proteins encoding a SpyTag. Here we show that SpyCatcher can be immobilized covalently on GNPs through GST without the loss of its full functionality. We then show that GST-SpyCatcher activated particles are able to covalently bind a SpyTag modified protein by simple mixing, through the spontaneous formation of an unusual isopeptide bond
Matter in Strong Magnetic Fields
The properties of matter are significantly modified by strong magnetic
fields, Gauss (), as are typically
found on the surfaces of neutron stars. In such strong magnetic fields, the
Coulomb force on an electron acts as a small perturbation compared to the
magnetic force. The strong field condition can also be mimicked in laboratory
semiconductors. Because of the strong magnetic confinement of electrons
perpendicular to the field, atoms attain a much greater binding energy compared
to the zero-field case, and various other bound states become possible,
including molecular chains and three-dimensional condensed matter. This article
reviews the electronic structure of atoms, molecules and bulk matter, as well
as the thermodynamic properties of dense plasma, in strong magnetic fields,
. The focus is on the basic physical pictures and
approximate scaling relations, although various theoretical approaches and
numerical results are also discussed. For the neutron star surface composed of
light elements such as hydrogen or helium, the outermost layer constitutes a
nondegenerate, partially ionized Coulomb plasma if , and may be in
the form of a condensed liquid if the magnetic field is stronger (and
temperature K). For the iron surface, the outermost layer of the
neutron star can be in a gaseous or a condensed phase depending on the cohesive
property of the iron condensate.Comment: 45 pages with 9 figures. Many small additions/changes. Accepted for
publication in Rev. Mod. Phy
Identifying a Window of Vulnerability during Fetal Development in a Maternal Iron Restriction Model
It is well acknowledged from observations in humans that iron deficiency during pregnancy can be associated with a number of developmental problems in the newborn and developing child. Due to the obvious limitations of human studies, the stage during gestation at which maternal iron deficiency causes an apparent impairment in the offspring remains elusive. In order to begin to understand the time window(s) during pregnancy that is/are especially susceptible to suboptimal iron levels, which may result in negative effects on the development of the fetus, we developed a rat model in which we were able to manipulate and monitor the dietary iron intake during specific stages of pregnancy and analyzed the developing fetuses. We established four different dietary-feeding protocols that were designed to render the fetuses iron deficient at different gestational stages. Based on a functional analysis that employed Auditory Brainstem Response measurements, we found that maternal iron restriction initiated prior to conception and during the first trimester were associated with profound changes in the developing fetus compared to iron restriction initiated later in pregnancy. We also showed that the presence of iron deficiency anemia, low body weight, and changes in core body temperature were not defining factors in the establishment of neural impairment in the rodent offspring
Fluency disorder or Asperger Syndrom?
Kinder mit Asperger Syndrom (AS) werden häufig zu spät oder fehldiagnostiziert und damit auch fehltherapiert. Die Diagnose eines AS innerhalb der phoniatrischen Ambulanz wird dadurch erschwert, dass die Kernsymptome, die sozialkommunikativen Auffälligkeiten, auch als Folgeerscheinung bei Sprachentwicklungsverzögerung (SEV) und Stottern/Poltern auftreten können. Bezüglich des Kriteriums "gestörte Sprachentwicklung" herrschen in der Literatur zum Asperger Syndrom divergente Auffassungen. Auch wird "Stottern/Poltern" als Symptom innerhalb des autistischen Spektrums nur am Rande erwähnt. Dennoch finden wir unter den phoniatrischen Störungsbildern immer wieder einzelne Fälle, bei denen Redeflussstörungen im Zusammenhang mit AS auftreten. Anhand von Videoaufzeichnungen werden in dem Vortrag die sprachlichen Symptome bei AS spezifiziert und die differentialdiagnostischen Kriterien aufgezeigt, anhand derer die Redeflussstörung innerhalb des autistischen Spektrums von isoliertem Stottern/Poltern zu unterscheiden sind. Diese Kriterien beziehen sich auf inhaltsanalytische Aspekte der Sprache und auf die anamnestischen Daten
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