214,029 research outputs found
Well-Composed Cell Complexes
Well-composed 3D digital images, which are 3D binary digital images whose boundary surface is made up by 2D manifolds, enjoy important topological and geometric properties that turn out to be advantageous for some applications. In this paper, we present a method to transform the cubical complex associated to a 3D binary digital image (which is not generally a well-composed image) into a cell complex that is homotopy equivalent to the first one and whose boundary surface is composed by 2D manifolds. This way, the new representation of the digital image can benefit from the application of algorithms that are developed over surfaces embedded in â3
Strong Euler well-composedness
In this paper, we define a new flavour of well-composedness, called strong Euler well composedness. In the general setting of regular cell complexes, a regular cell complex of dimension n is strongly Euler well-composed if the Euler characteristic of the link of each boundary cell is 1, which is the Euler characteristic of an (nâ1)-dimensional ball. Working in the particular setting of cubical complexes canonically associated with nD pictures, we formally prove in this paper that strong Euler well-composedness implies digital well-composedness in any dimension n â„ 2 and that the converse is not true when n â„ 4Ministerio de Ciencia, InnovaciĂłn y Universidades PID2019-107339GB-I00Junta de AndalucĂa P20_0114
EVOLUTION OF PROTEIN COMPLEXES IN BACTERIAL SPECIES
Protein complexes are composed of two or more associated polypeptide chains that may have different functions. Protein complexes play a critical role for all processes in life and are considered as highly conserved in evolution. In previous studies, protein complexes from E. coli or Mycoplasma pneumoniae have been characterized experimentally, revealing that a typical bacterial cell has on the order of 500 protein complexes. Using gene homology (orthology), these experimentally-observed complexes can be used to predict protein complexes across many species of bacteria. Surprisingly, the majority of protein complexes is not conserved, demonstrating an unexpected evolutionary flexibility.
The current research investigates the evolution of 174 well-characterized (âreferenceâ) protein complexes from E. coli that have three or more subunits. More specifically, we study the evolutionary flexibility by using evidence and patterns of the presence or absence of the subunits across a range of 894 bacterial species and to interpret whether the evolution is due to the loss or gain of a subunit in the protein complex. The purpose of this study is to determine how the presence or absence of a subunit affects the protein complexesâ functionality. We discuss the functional changes observed in a protein complex due to the presence or absence of a particular subunit by using a statistical approach and by confirming its significance.https://scholarscompass.vcu.edu/uresposters/1253/thumbnail.jp
Efficiently Storing Well-Composed Polyhedral Complexes Computed Over 3D Binary Images
A 3D binary image I can be naturally represented
by a combinatorial-algebraic structure called cubical complex
and denoted by Q(I ), whose basic building blocks are
vertices, edges, square faces and cubes. In Gonzalez-Diaz
et al. (Discret Appl Math 183:59â77, 2015), we presented a
method to âlocally repairâ Q(I ) to obtain a polyhedral complex
P(I ) (whose basic building blocks are vertices, edges,
specific polygons and polyhedra), homotopy equivalent to
Q(I ), satisfying that its boundary surface is a 2D manifold.
P(I ) is called a well-composed polyhedral complex over the
picture I . Besides, we developed a new codification system
for P(I ), encoding geometric information of the cells
of P(I ) under the form of a 3D grayscale image, and the
boundary face relations of the cells of P(I ) under the form
of a set of structuring elements. In this paper, we build upon
(Gonzalez-Diaz et al. 2015) and prove that, to retrieve topological
and geometric information of P(I ), it is enough to
store just one 3D point per polyhedron and hence neither
grayscale image nor set of structuring elements are needed.
From this âminimalâ codification of P(I ), we finally present
a method to compute the 2-cells in the boundary surface of
P(I ).Ministerio de EconomĂa y Competitividad MTM2015-67072-
3D Well-composed Polyhedral Complexes
A binary three-dimensional (3D) image is well-composed if the boundary
surface of its continuous analog is a 2D manifold. Since 3D images are not
often well-composed, there are several voxel-based methods ("repairing"
algorithms) for turning them into well-composed ones but these methods either
do not guarantee the topological equivalence between the original image and its
corresponding well-composed one or involve sub-sampling the whole image.
In this paper, we present a method to locally "repair" the cubical complex
(embedded in ) associated to to obtain a polyhedral
complex homotopy equivalent to such that the boundary of every
connected component of is a 2D manifold. The reparation is performed via
a new codification system for under the form of a 3D grayscale image
that allows an efficient access to cells and their faces
Encoding Specific 3D Polyhedral Complexes Using 3D Binary Images
We build upon the work developed in [4] in which we presented
a method to âlocally repairâ the cubical complex Q(I) associated
to a 3D binary image I, to obtain a âwell-composedâ polyhedral complex
P(I), homotopy equivalent to Q(I). There, we developed a new codification
system for P(I), called ExtendedCubeMap (ECM) representation,
that encodes: (1) the (geometric) information of the cells of P(I) (i.e.,
which cells are presented and where), under the form of a 3D grayscale
image gP ; (2) the boundary face relations between the cells of P(I),
under the form of a set BP of structuring elements.
In this paper, we simplify ECM representations, proving that geometric
and topological information of cells can be encoded using just a 3D
binary image, without the need of using colors or sets of structuring
elements. We also outline a possible application in which well-composed
polyhedral complexes can be useful.Junta de AndalucĂa FQM-369Ministerio de EconomĂa y Competitividad MTM2012-32706Ministerio de EconomĂa y Competitividad MTM2015-67072-
A practical method for efficient and optimal production of Selenoâmethionineâlabeled recombinant protein complexes in the insect cells
The use of Selenoâmethionine (SeMet) incorporated protein crystals for single or multiâwavelength anomalous diffraction (SAD or MAD) to facilitate phasing has become almost synonymous with modern Xâray crystallography. The anomalous signals from SeMets can be used for phasing as well as sequence markers for subsequent model building. The production of large quantities of SeMet incorporated recombinant proteins is relatively straightforward when expressed in Escherichia coli. In contrast, production of SeMet substituted recombinant proteins expressed in the insect cells is not as robust due to the toxicity of SeMet in eukaryotic systems. Previous protocols for SeMetâincorporation in the insect cells are laborious, and more suited for secreted proteins. In addition, these protocols have generally not addressed the SeMet toxicity issue, and typically result in low recovery of the labeled proteins. Here we report that SeMet toxicity can be circumvented by fully infecting insect cells with baculovirus. Quantitatively controlling infection levels using our Titer Estimation of Quality Control (TEQC) method allow for the incorporation of substantial amounts of SeMet, resulting in an efficient and optimal production of labeled recombinant protein complexes. With the method described here, we were able to consistently reach incorporation levels of about 75% and protein yield of 60â90% compared with native protein expression
Neuro-Insular Complexes in the Human Pancreas
It is well known that pancreatic islets are complex structures composed of endodermally derived endocrine cells, integrated with endothelial cells and other cells, originating from the mesoderm, and innervated by nerve fibers that have a neuroectodermal origin. In our studies, we focused on the interactions between the structures of the nervous system and endocrine cells, the so-called neuro-insular complexes, in the human pancreas. In this chapter, we present our results and literature data concerning the morphological organization of neuro-insular complexes in humans and other mammals. We also discuss the possible functional role of neuro-insular complexes, such as the involvement of the nervous system in the regulation and synchronization of islet hormone secretion and the morphogenetic plasticity of the endocrine pancreas in adults, as well as in the regulation of endocrine cell proliferation and maturation during prenatal development of the pancreas
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