Enhancement of the antioxidant and antimicrobial activities of porphyran through chemical modification with tyrosine derivatives

The chemical modification of porphyran hydrocolloid is attempted, with the objective of enhancing its antioxidant and antimicrobial activities. Sulfated galactan porphyran is obtained from commercial samples of the red algae Porphyra dioica using Soxhlet extraction with water at 100ºC and precipitation with isopropyl alcohol. The extracted porphyran is then treated with modified L-tyrosines in aqueous medium in the presence of NaOH, at ca. 70ºC. The modified tyrosines L1 and L2 are prepared through a Mannich reaction with either thymol or 2,4-di-tert-butylphenol, respectively. While the reaction with 2,4-di-tert-butylphenol yields the expected tyrosine derivative, a mixture of products is obtained with thymol. The resulting polysaccharides are structurally characterized and the respective antioxidant and antimicrobial activities are determined. Porphyran treated with the N-(2-hydroxy-3,5-di-tert-butyl-benzyl)-L-tyrosine derivative, POR-L2, presents a noticeable superior radical scavenging and antioxidant activity compared to native porphyran, POR. Furthermore, it exhibited some antimicrobial activity against S. aureus. The surface morphology of films prepared by casting with native and modified porphyrans is studied by SEM/EDS. Both POR and POR-L2 present potential applicability in the production of films and washable coatings for food packaging with improved protecting characteristics.info:eu-repo/semantics/publishedVersio

Entanglement molecules

We investigate the entanglement properties of multiparticle systems, concentrating on the case where the entanglement is robust against disposal of particles. Two qubits -belonging to a multipartite system- are entangled in this sense iff their reduced density matrix is entangled. We introduce a family of multiqubit states, for which one can choose for any pair of qubits independently whether they should be entangled or not as well as the relative strength of the entanglement, thus providing the possibility to construct all kinds of ''Entanglement molecules''. For some particular configurations, we also give the maximal amount of entanglement achievable.Comment: 4 pages, 1 figur

Borromean molecules

For some values of the constituent masses m_i, the hydrogen-like molecule (m_1^+,m_2^+,m_3^-,m_4^-) is stable with respect to spontaneous dissociation into two neutral atoms, while none of its three-body subsystems such as (m_1^+,m_2^+,m_3^-) is stable. This occurs in particular in the neighbourhood of the (M^+,m^+,M^-,m^-) configuration with M/m=2, as for instance for the molecule (p,d,\bar{p},\bar{d}) involving an antiproton and an antideuteron.Comment: 3 pages, Talk given at the XVIII European Few-Body Conference, Bled, Slovenia, September 2002, to app. in Few-Body Sys. Supp

Parabolic Molecules

Anisotropic decompositions using representation systems based on parabolic scaling such as curvelets or shearlets have recently attracted significantly increased attention due to the fact that they were shown to provide optimally sparse approximations of functions exhibiting singularities on lower dimensional embedded manifolds. The literature now contains various direct proofs of this fact and of related sparse approximation results. However, it seems quite cumbersome to prove such a canon of results for each system separately, while many of the systems exhibit certain similarities. In this paper, with the introduction of the notion of {\em parabolic molecules}, we aim to provide a comprehensive framework which includes customarily employed representation systems based on parabolic scaling such as curvelets and shearlets. It is shown that pairs of parabolic molecules have the fundamental property to be almost orthogonal in a particular sense. This result is then applied to analyze parabolic molecules with respect to their ability to sparsely approximate data governed by anisotropic features. For this, the concept of {\em sparsity equivalence} is introduced which is shown to allow the identification of a large class of parabolic molecules providing the same sparse approximation results as curvelets and shearlets. Finally, as another application, smoothness spaces associated with parabolic molecules are introduced providing a general theoretical approach which even leads to novel results for, for instance, compactly supported shearlets

Phosphonopeptides Revisited, in an Era of Increasing Antimicrobial Resistance

Given the increase in resistance to antibacterial agents, there is an urgent need for the development of new agents with novel modes of action. As an interim solution, it is also prudent to reinvestigate old or abandoned antibacterial compounds to assess their efficacy in the context of widespread resistance to conventional agents. In the 1970s, much work was performed on the development of peptide mimetics, exemplified by the phosphonopeptide, alafosfalin. We investigated the activity of alafosfalin, di-alanyl fosfalin and β-chloro-L-alanyl-β-chloro-L-alanine against 297 bacterial isolates, including carbapenemase-producing Enterobacterales (CPE) (n = 128), methicillin-resistant Staphylococcus aureus (MRSA) (n = 37) and glycopeptide-resistant enterococci (GRE) (n = 43). The interaction of alafosfalin with meropenem was also examined against 20 isolates of CPE. The MIC50 and MIC90 of alafosfalin for CPE were 1 mg/L and 4 mg/L, respectively and alafosfalin acted synergistically when combined with meropenem against 16 of 20 isolates of CPE. Di-alanyl fosfalin showed potent activity against glycopeptide-resistant isolates of Enterococcus faecalis (MIC90; 0.5 mg/L) and Enterococcus faecium (MIC90; 2 mg/L). Alafosfalin was only moderately active against MRSA (MIC90; 8 mg/L), whereas β-chloro-L-alanyl-β-chloro-L-alanine was slightly more active (MIC90; 4 mg/L). This study shows that phosphonopeptides, including alafosfalin, may have a therapeutic role to play in an era of increasing antibacterial resistance

Producing translationally cold, ground-state CO molecules

Carbon monoxide molecules in their electronic, vibrational, and rotational ground state are highly attractive for trapping experiments. The optical or ac electric traps that can be envisioned for these molecules will be very shallow, however, with depths in the sub-milliKelvin range. Here we outline that the required samples of translationally cold CO (X$^1\Sigma^+$, $v"$=0, $N"$=0) molecules can be produced after Stark deceleration of a beam of laser-prepared metastable CO (a$^3\Pi_1$) molecules followed by optical transfer of the metastable species to the ground state \emph{via} perturbed levels in the A$^1\Pi$ state. The optical transfer scheme is experimentally demonstrated and the radiative lifetimes and the electric dipole moments of the intermediate levels are determined