Biomedical subjects

Andrea Motta

Publications and source records attributed to Andrea Motta.

27 records · Page 2Linked to original sources

PubMed2003

Two distinct calcium-calmodulin interactions with N-terminal regions of the olfactory and rod cyclic nucleotide-gated channels characterized by NMR spectroscopy.

The interactions of calcium-calmodulin with two fragments of the N-terminal domains of the olfactory alpha-subunit and rod beta-subunit cyclic nucleotide-gated channels have been investigated using nuclear magnetic resonance spectroscopy. The results indicate that in the two cases both the N-terminal and the C-terminal calmodulin lobes are involved in the interaction. The olfactory cyclic nucleotide-gated channel segment forms a 1:1 complex with calmodulin, whereas the rod fragment forms a 2:1 complex. The correlation times of the two complexes, as estimated by (15)N relaxation studies, are compatible with the observed stoichiometries. These results indicate differences in the mode of action by which calmodulin modulates the activity of both channels, and suggest either that the rod channel is modulated through a simultaneous interaction of two beta-subunits with calmodulin or that other regions of the N-terminus are necessarily implicated in the binding.

Amino Acid Sequence↗

PubMed2003

Diplopyrone, a new phytotoxic tetrahydropyranpyran-2-one produced by Diplodia mutila, a fungus pathogen of cork oak.

A new phytotoxic monosubstituted tetrahydropyranpyran-2-one, named diplopyrone (1), was isolated from the liquid culture filtrates of Diplodia mutila, a plant pathogenic fungus causing a form of canker disease of cork oak (Quercus suber). Diplopyrone was characterized, using spectroscopic and chemical methods, as 6-[(1S)-1-hydroxyethyl]-2,4a,6,8a-tetrahydropyran[3,2-b]pyran-2-one. The absolute stereochemistry of the chiral secondary hydroxylated carbon (C-9), determined by application of Mosher's method, proved to be S. Diplopyrone assayed at a 0.01-0.1 mg/mL concentration range caused necrosis and wilting on cork oak cuttings. On a nonhost plant, tomato, diplopyrone caused brown discoloration or stewing on the stem.

Italy↗

PubMed2003

Cytochalasins Z4, Z5, and Z6, three new 24-Oxa[14]cytochalasans produced by Phoma exigua var. heteromorpha.

Cytochalasins Z4, Z5, and Z6, three new cytochalasans, were isolated from the wheat culture of Phoma exigua var. heteromorpha together with the known cytochalasins A, B, F, T, Z2, and Z3, 7-O-acetylcytochalasin B, and deoxaphomin. Z2 and Z3, together with Z1, have recently been described as new 24-oxa[14]cytochalasans produced by Pyrenophora semeniperda, a fungus proposed for biological control of grass weeds. All three new cytochalasins were characterized as 24-oxa[14]cytochalasans by extensive use of NMR and MS techniques. Cytochalasins Z4 and Z5 proved to be structurally related to cytochalasin B, whereas Z6 was related to cytochalasin F. When assayed on tomato seedlings at 10(-4) M, Z6 caused a very low inhibition of rootlet elongation (30%), whereas Z4 and Z5 were almost inactive. On brine shrimp, at the same concentration, only Z5 had a minor effect, with 20% mortality, whereas the other two metabolites proved to be inactive.

Animals↗

PubMed2002

SDS-resistant active and thermostable dimers are obtained from the dissociation of homotetrameric beta-glycosidase from hyperthermophilic Sulfolobus solfataricus in SDS. Stabilizing role of the A-C intermonomeric interface.

beta-Glycosidases are fundamental, widely conserved enzymes. Those from hyperthermophiles exhibit unusual stabilities toward various perturbants. Previous work with homotetrameric beta-glycosidase from hyperthermophilic Sulfolobus solfataricus (M(r) 226,760) has shown that addition of 0.05-0.1% SDS was associated with minimal secondary structure perturbations and increased activity. This work addresses the effects of SDS on beta-glycosidase quaternary structure. In 0.1-1% SDS, the enzyme was dimeric, as determined by Ferguson analysis of transverse-gradient polyacrylamide gels. The catalytic activity of the beta-glycosidase dimer in SDS was determined by in-gel assay. A minor decrease of thermal stability in SDS was observed after exposure to temperatures up to 80 degrees C for 1 h. An analysis of beta-glycosidase crystal structure showed different changes in solvent-accessible surface area on going from the tetramer to the two possible dimers (A-C and A-D). Energy minimization and molecular dynamics calculations showed that the A-C dimer, exhibiting the lowest exposed surface area, was more stabilized by a network of polar interactions. The charge distribution around the A-C interface was characterized by a local short range anisotropy, resulting in an unfavorable interaction with SDS. This paper provides a detailed description of an SDS-resistant inter-monomeric interface, which may help understand similar interfaces involved in important biological processes.

Binding Sites↗

PubMed2002

A new time-domain frequency-selective quantification algorithm.

In this paper a new time-domain frequency-selective quantification algorithm is presented. Frequency-selective quantification refers to a method that analyzes spectral components in a selected frequency region, ignoring all the other components outside. The algorithm, referred to as MeFreS (Metropolis Frequency-Selective), is based on rank minimization of an opportune Hankel matrix. The minimization procedure is satisfied by the down-hill simplex method, implemented with the simulated annealing method. MeFreS does not use any preprocessing step or filter to suppress nuisance peaks, but the signal model function is directly fitted. In this manner, neither inherent signal distortions nor estimation biases to be corrected occur. The algorithm was tested with Monte Carlo simulations. A comparison with VARPRO and AMARESw algorithms was carried out. Finally, two samples of known content from NMR data were quantified.

Algorithms↗

PubMed2002

Sphaeropsidins D and E, two other pimarane diterpenes, produced in vitro by the plant pathogenic fungus Sphaeropsis sapinea f. sp. cupressi.

Two pimarane diterpenes structurally related to sphaeropsidins were isolated from the liquid culture of Sphaeropsis sapinea f. sp. cupressi, a plant pathogenic fungus causing a form of canker disease of Italian cypress (Cupressus sempervirens L.). The two metabolites, characterised by spectroscopic methods, were named sphaeropsidins D (0.40 mg l(-1)) and E (0.16 mg l(-1)). The same fungus produced sphaeropsidins A, B and C, sphaeropsidone and episphaeropsidone, which proved to be phytotoxic to cypress, and chlorosphaeropsidone and epichlorosphaeropsidone showing no phytotoxicity. Sphaeropsidin D assayed at 0.1 mg ml(-1) on severed cypress twigs caused leaf browning and necrosis on Cupressus macrocarpa, but no symptoms were observed on C. sempervirens and C. arizonica. Symptoms appeared in a period of time (6 days after toxin-treatment) shorter than that for sphaeropsidin A. Sphaeropsidin E assayed at 0.2 mg ml(-1) did not produce any symptom on the same cypress species tested with sphaeropsidin D.

Biological Assay↗

PubMed2002

Cytochalasins Z1, Z2 and Z3, three 24-oxa[14]cytochalasans produced by Pyrenophora semeniperda.

Three new cytochalasans, named cytochalasins Z1, Z2 and Z3, were isolated from the wheat culture of Pyrenophora semeniperda, a fungus proposed to biologically control grass weeds. Other cytochalasins isolated from the same organic extract were identified as the already known cytochalasins F, T, deoxaphomin and cytochalasins B, the latter being produced in very large amounts. All three new cytochalasins were characterized as 24-oxa[14]cytochalasans by extensive use of NMR and MS techniques. Cytochalasins Z1 and Z2 proved to be structurally related to cytochalasin T, whereas cytochalasin Z3 was related to cytochalasin B. When assayed on wheat and tomato seedlings, cytochalasin Z3, in comparison to the new cytochalasins, cytochalasin B, its 21,22-dihydroderivative, cytochalasin F and deoxaphomin showed a remarkable ability to inhibit root elongation. The possibility of using these metabolites in biological control strategies is discussed.

Cytochalasins↗

PubMed2002

The cytoplasmic tail of invariant chain regulates endosome fusion and morphology.

The major histocompatibility complex class II associated invariant chain (Ii) has been shown to inhibit endocytic transport and to increase the size of endosomes. We have recently found that this property has a significant impact on antigen processing and presentation. Here, we show in a cell-free endosome fusion assay that expression of Ii can increase fusion after phosphatidylinositol 3-kinase activity is blocked by wortmannin. In live cells wortmannin was also not able to block formation of the Ii-induced enlarged endosomes. The effects of Ii on endosomal transport and morphology depend on elements within the cytoplasmic tail. Data from mutagenesis analysis and nuclear magnetic resonance-based structure calculations of the Ii cytoplasmic tail demonstrate that free negative charges that are not involved in internal salt bridges are essential for both interactions between the tails and for the formation of enlarged endosomes. This correlation indicates that it is interactions between the Ii cytoplasmic tails that are involved in endosome fusion. The combined data from live cells, cell-free assays, and molecular dynamic simulations suggest that Ii molecules on different vesicles can promote endosome docking and fusion and thereby control endosomal traffic of membrane proteins and endosomal content.

Amino Acid Sequence↗

PubMedDate not supplied

1H-NMR evidence for a different response to the same dose (2 Gy) of ionizing radiation of MG-63 human osteosarcoma cells and three-dimensional spheroids.

High resolution proton nuclear magnetic resonance (1H-NMR) spectroscopy was used to examine the response of the MG-63 osteosarcoma cell line grown in monolayer and as 3-dimensional tumor spheroids to the same low dose (2 Gy) of ionizing radiation. The MG-63 cells and spheroids were irradiated at 24 h of growth and the 1H-NMR spectra of whole control and irradiated monolayer cells and of whole control and irradiated multicellular spheroids collected after another 24 h were compared. The 1H-NMR spectra of the perchloric acid extracts as well as the 2-dimensional 1H-NMR spectra of both pairs of cell systems were also obtained. Possible radiation-induced cell damage was determined by lactate dehydrogenase (LDH) release and variations in cell growth, while cell death was evaluated by chromatin dye Hoechst staining and DNA fragmentation assays. The results demonstrated that no cell damage took place, but that significant variations in numerous metabolites occured in both the monolayer cells and the spheroids after irradiation. Most of the changes observed were very similar in nature. In fact, significant increases in lactate, alanine, creatine and phosphocreatine and choline-containing metabolites and a significant decrease in glutathione (GSH) were observed in both cells and spheroids. However, while significant increases in CH2 and CH3 mobile lipids, glutamine/glutamate, taurine and inositol were seen in the spheroids, no variations in CH2 or CH3 lipids, glutamine/glutamate or taurine were recorded in the MG-63 cells grown in monolayer after irradiation. In addition, a significant decrease rather than a significant increase in inositol was also noted in the monolayer cells. The data presented seem to suggest that, although neither monolayer cells nor spheroids show apparent signs of damage after exposure to the same dose of ionizing radiation, very different cell death responses as well as very diverse antioxidant/osmoregulatory reactions were triggered by this stressing agent.

Bone Neoplasms↗