2,428 research outputs found
Energy spectra of two interacting fermions with spin-orbit coupling in a harmonic trap
We explore the two-body spectra of spin- fermions in isotropic harmonic
traps with external spin-orbit potentials and short range two-body
interactions. Using a truncated basis of total angular momentum eigenstates,
non-perturbative results are presented for experimentally realistic forms of
the spin-orbit coupling: a pure Rashba coupling, Rashba and Dresselhaus
couplings in equal parts, and a Weyl-type coupling. The technique is easily
adapted to bosonic systems and other forms of spin-orbit coupling.Comment: 12 pages, 9 figure
ANTI-STAPHYLOCOCCAL BIOFILM ACTIVITY OF NOVEL SORTASE A (SRTA) INHIBITORS
Pathogenic staphylococci have an extraordinary ability to form biofilms. This characteristic is likely the most important
virulence factor of staphylococci in the development of the chronic form of infectious diseases and in biomaterial
associated infections (BAI). Staphylococcal biofilms are particularly dangerous because they are more resistant to host
immune defence system and have a significantly increased tolerance to conventional antibiotics. There is undoubtedly an
urgent need for novel treatments, strategies and anti-staphylococcal biofilm agents.
The Sortase A (SrtA) transpeptidase is responsible for covalent anchoring to the cell wall of various surface proteins
(FnbpA, FnbpB, ClfA, ClfB, Protein A, etc.) that have a direct role in the pathogenesis and in the first stage of biofilm
formation and because of this it can be considered a good target candidate to design agents that could interfere with
virulence mechanism including biofilm formation.
With the aim to discover new SrtA inhibitors, a library of 50000 low-molecular weight compounds was screened in a high
throughput assay by using the standard Dabcyl-QALPETGEE-Edans fluorescence resonance energy transfer (FRET)-
peptide substrate for measurement of enzyme activity. A group of the selected 38 most potent compounds and 3 known
reference inhibitors were further evaluated in an in vitro biofilm formation assay at a screening concentration of 10\ub5g/ml
using three reference staphylococcal strains S.aureus 29213, 6538 and S.epidermidis RP62A.
An interesting correlation between inhibition of SrtA and biofilm formation inhibition was observed in many cases
especially at a concentration equal or more than IC50 determined as SrtA inhibitors
Non-covalent interactions in organotin(IV) derivatives of 5,7-ditertbutyl- and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine as recognition motifs in crystalline self- assembly and their in vitro antistaphylococcal activity
Non-covalent interactions are known to play a key role in biological compounds due to their
stabilization of the tertiary and quaternary structure of proteins [1]. Ligands similar to purine rings,
such as triazolo pyrimidine ones, are very versatile in their interactions with metals and can act as
model systems for natural bio-inorganic compounds [2]. A considerable series (twelve novel
compounds are reported) of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) and 5,7-diphenyl-
1,2,4-triazolo[1,5-a]pyrimidine (dptp) were synthesized and investigated by FT-IR and 119Sn
M\uf6ssbauer in the solid state and by 1H and 13C NMR spectroscopy, in solution [3]. The X-ray
crystal and molecular structures of Et2SnCl2(dbtp)2 and Ph2SnCl2(EtOH)2(dptp)2 were described, in
this latter pyrimidine molecules are not directly bound to the metal center but strictly H-bonded,
through N(3), to the -OH group of the ethanol moieties. The network of hydrogen bonding and
aromatic interactions involving pyrimidine and phenyl
rings in both complexes drives their self-assembly. Noncovalent
interactions involving aromatic rings are key
processes in both chemical and biological recognition,
contributing to overall complex stability and forming
recognition motifs. It is noteworthy that in
Ph2SnCl2(EtOH)2(dptp)2 \u3c0\u2013\u3c0 stacking interactions between
pairs of antiparallel triazolopyrimidine rings mimick basepair
interactions physiologically occurring in DNA (Fig.1).
M\uf6ssbauer spectra suggest for Et2SnCl2(dbtp)2 a
distorted octahedral structure, with C-Sn-C bond angles
lower than 180\ub0. The estimated angle for Et2SnCl2(dbtp)2
is virtually identical to that determined by X-ray diffraction. Ph2SnCl2(EtOH)2(dptp)2 is
characterized by an essentially linear C-Sn-C fragment according to the X-ray all-trans structure.
The compounds were screened for their in vitro antibacterial activity on a group of reference
staphylococcal strains susceptible or resistant to methicillin and against two reference Gramnegative
pathogens [4] . We tested the biological activity of all the specimen against a group of
staphylococcal reference strains (S. aureus ATCC 25923, S. aureus ATCC 29213, methicillin
resistant S. aureus 43866 and S. epidermidis RP62A) along with Gram-negative pathogens (P.
aeruginosa ATCC9027 and E. coli ATCC25922). Ph2SnCl2(EtOH)2(dptp)2 showed good
antibacterial activity with a MIC value of 5 \u3bcg mL-1 against S. aureus ATCC29213 and also
resulted active against methicillin resistant S. epidermidis RP62A
Fragments of -thymosin from the sea urchin Paracentrotus lividus as potential antimicrobial peptides against staphylococcal biofilms
The immune mediators in echinoderms can be a potential source of novel antimicrobial peptides (AMPs) applied
toward controlling pathogenic staphylococcal biofilms that are intrinsically resistant to conventional antibiotics.
The peptide fraction <5 kDa from the cytosol of coelomocytes of the sea urchin Paracentrotus lividus (5-CC)
was tested against a group of Gram-positive and Gram-negative pathogen reference strains. The 5-CC of P. lividus
was active against all planktonic-tested strains but also showed antibiofilm properties against staphylococcal strains.
Additionally,wedemonstrated the presenceof three smallpeptides in the5-CCbelonging tosegment 9-41of aP. lividus
-thymosin. The smallest of these peptides in particular, showed the common chemical\u2013physical characteristics of
AMPs. This novel AMP from -thymosin has high potential activity as an antibiofilm agent, acting on slow-growing
bacterial cells that exhibit a reduced susceptibility to conventional antibiotics and represent a reservoir for recurrent
biofilm-associated infections
A very promising antibiofilm activity against Candida albicans from an in vitro screening for antimicrobial, antibiofilm and antiproliferative activity of new synthesized 4-cinnamamido- and 2-phenoxyacedamido-1H-pyrazol-5-yl)benzamides
Several new synthesized 4-cinnamamido- and 2-phenoxyacedamido-(1H-pyrazol-5-yl)benzamides were obtained by two
multi step different synthetic routes in order to maximize their yield. The new derivatives were screened to determine the
antiproliferative, antimicrobial and antibiofilm activity. The biological results showed how, respect to the antiproliferative
and antimicrobial activities, the compounds have a low to missing activity. Different are the results obtained concerning the
antibiofilm activity, especially towards Candida albicans. Most of the synthesized compounds showed a good percentage
inhibition of biofilm formation ranging from 60 to 73% with a Biofilm Inhibition Concentration 50% (BIC50) from 0.13 to
0.01 μM. Among the synthesized compounds the ethyl 5-(4-(2-(4-chlorophenoxy)acetamido)benzamido)-1-methyl-1Hpyrazole-
4-carboxylate (27c) resulted the most active molecule with a BIC50 of 0.01 μM. According to the results obtained,
such compound could be considered a lead subject of further studies to obtain novel and more effective antibiofilm agents
against C. albicans
De novo design of antimicrobial and antibiofilm peptides starting from desert truffle Tirmania pinoyi peptides
With the aim of discovering new routes in the research of antimicrobials, we focused on polypeptide-
enriched extracts derived from edible desert truffle mushroom Tirmania pinoyi. The extracts
showed an interesting activity with MIC=50 μg/mL against Staphylococcus aureus ATCC 29213
and Pseudomonas aeruginosa ATCC 15442. Through mass spectrometry analysis (RP-HPLC/
nESI-MS/MS) the following eight novel peptides FDVVPKTAANFRAL, AVTVGASTLADERA,
FLVGGASLKPEF, VARIFAVFNDTF, HLVDEPQNLLK, LGEYGFQNALLR, FAVNGGCAKET,
SREDLHPKL were detected. To characterize them online websites were used: IAMPpred,
DPBAAS, Cell-PPD, ToxinPred, HemoPI, PeptideCutter and HLP. The analysis indicated that
some peptides showed negative or neutral charge, hydrophobic ratio between 42% and 67%,
Boman Index < 2.25 kCal/mol. According to the “APD3: Antimicrobial Peptide Calculator and
Predictor” tool of the Antimicrobial Peptide Database (APD) similarities (around 30-40%) with
known antimicrobial peptides (AMPs) identified in amphibians were also detected. In contrast, the
predicted antimicrobial, antifungal and antibiofilm activity was not significant.
In order to improve biological and physico-chemical properties, the sequences of natural peptides
were modified using APD3, by replacing some hydrophilic and negative charged amino acids
with hydrophobic and positive ones. The derivative sequences (GWDVVPKTWWKFRAL,
KWTWGASTLAKKRA, FLRGGWSLKPKF, KWRIFWVFNKTF, HLVKRWQNLLK,
KGKYRFWNALLR, FARWGGCAKRT, SRKWLHPWL) showed net positive charge between
+2 and +4, hydrophobic ratio between 42% and 48%, Boman Index < 2.25 kCal/mol and high
stability. Moreover, the predicted antimicrobial, antifungal and antibiofilm activity was high, without
toxic or hemolytic effects.
In conclusion, bioinformatic analysis has demonstrated that novel peptides discovered in T. pinoyi
may be considered new platforms for the design of novel antimicrobial and antibiofilm peptides to
counteract multi-drug resistant pathogens
Assessment of energy return on energy investment (EROEI) of oil bearing crops for renewable fuel production
As reported in literature the production of biodiesel should lead to a lower energy consumption than those obtainable with its use. So, to justify its consumption, a sustainable and “low input” production should be carried out. In order to assess the sustainability of Linum usitatissimum, Camelina sativa and Brassica carinata cultivation for biodiesel production in terms of energy used compared to that obtained, the index EROEI (Energy Return On Energy Invested) has been used. At this aim, an experimental field was realised in the south-eastern Sicilian land. During the autumn-winter crop cycle, no irrigation was carried out and some suitable agricultural practices have been carried out taking into account the peculiarity of each type of used seeds. The total energy consumed for the cultivation of oil bearing crops from sowing to the production of biodiesel represents the Input of the process. In particular, this concerned the energy embodied in machinery and tools utilized, in seed, chemical fertilizer and herbicide but also the energy embodied in diesel fuels and lubricant oils. In addition, the energy consumption relating to machines and reagents required for the processes of extraction and transesterification of the vegetable oil into biodiesel have been calculated for each crops. The energy obtainable from biodiesel production, taking into account the energy used for seed pressing and for vegetable oil transesterification into biodiesel, represents the Output of the process. The ratio Output/Input gets the EROEI index which in the case of Camelina sativa and Linum usatissimum is greater than one. These results show that the cultivation of these crops for biofuels production is convenient in terms of energy return on energy investment. The EROEI index for Brassica carinata is lower than one. This could means that some factors, concerning mechanisation and climati
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