Viscosimetric studies on 2-methoxyethanol + 1,2-dimethoxyethane binary mixtures from −10 to 80°c

The kinematic viscosities (v) were measured for nine binary solvent mixtures of 2-methoxyethanol (ME) + 1,2-dimethoxyethane (DME) at nineteen temperatures ranging from ?10 to +80°C. The experimental data have been used to test some empirical equations of the type v = v(T), v = v(X₁) and v = v(T, X₁). The viscosities of all the mixtures increase from the values of pure DME to that of ME as the mole fraction of ME increases, and always yield a negative excess property (v^E) at all the investigated temperatures. Furthermore, thermodynamic parameters of viscous flow have been evaluated on the basis of the Eyring theory. The excess free energy of activation of viscous flow (ΔG^E) vs X₂ plot suggests the presence of a stable hetero-adduct, having ME : DME = 1 : 1 stoichiometric ratio.     

Optical properties of hybrid T3Pyr/SiO2/3C-SiC nanowires

A new class of nanostructured hybrid materials is developed by direct grafting of a model thiophene-based organic dye on the surface of 3C-SiC/SiO₂ core/shell nanowires. TEM-EDX analysis reveals that the carbon distribution is more spread than it would be, considering only the SiC core size, suggesting a main contribution from C of the oligothiophene framework. Further, the sulfur signal found along the treated wires is not detected in the as-grown samples. In addition, the fluorescent spectra are similar for the functionalized nanostructures and T3Pyr in solution, confirming homogeneous molecule grafting on the nanowire surface. Chemical and luminescence characterizations confirm a homogeneous functionalization of the nanowires. In particular, the fluorophore retains its optical properties after functionalization.     

A new three-parameter Corresponding States Model for pure Halocarbons Viscosity Prediction

Predictive and semipredictive models for viscosity calculation are currently needed and highly appreciated. Models developed for halogenated refrigerants (HR) and based on Corresponding States (CS) are leading to a prediction accuracy comparable to that of specifically developed models. In the present work, using recently published, highly accurate viscosity dedicated equations, it has been verified that viscosity conforms to a two-parameter CS model is then developed, based on Teja and coworker's three-parameter CS structure. Two fluids of the same family are taken for reference, and the reduced viscosity of a third fluid is obtained in reduced P,T variables. At first the Pitzer acentric factor is proposed as a third parameter, then it is substituted with a temperature-dependent function fitted on saturated viscosity data. The prediction accuracy of the model is comparable to that of the reference fluid equations and, considering its predictive nature, it is a satisfactory tool for the needs of technical applications.     

Gas phase complete catalytic oxidation of aromatic hydrocarbon mixtures

In this work oxidation of benzene and ethenylbenzene (IUPAC name for styrene) as single compounds and in binary mixtures over a Pt honeycomb catalyst were investigated. Both aromatic compounds showed zero-order kinetics over a wide concentration range. The ethenylbenzene reaction rate was affected weakly by the presence of benzene, whereas benzene oxidation was inhibited strongly by ethenylbenzene. The Mars-van Krevelen mechanism (which is generally accepted for single aromatic compound oxidation kinetics) gave rise to inconsistencies in describing mixture behaviour. A different kinetic model is proposed, where benzene reacts from the gas phase and ethenylbenzene is adsorbed on the catalyst competing with oxygen for active sites. This model was able to interpret the oxidation of mixtures quite satisfactorily.     

A cyclic CCK8 analogue selective for the cholecystokinin type A receptor: design, synthesis, NMR structure and binding measurements

A cyclic CCK8 analogue, cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 (Dpr=L-2,3-diaminopropionic acid), has been designed on the basis of the NMR structure of the bimolecular complex between the N-terminal fragment of the CCK(A) receptor and its natural ligand CCK8. The conformational features of cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 have been determined by NMR spectroscopy in aqueous solution and in water containing DPC-d(38) micelles (DPC=dodecylphosphocholine). The structure of the cyclic peptide in aqueous solution is found to be in a relaxed conformation, with the backbone and Dpr29 side chain atoms making a planar ring and the N-terminal tripeptide extending approximately along the plane of this ring. In DPC/water, the cyclic peptide adopts a "boat-shaped" conformation, which is more compact than that found in aqueous solution. The cyclic constraint between the Dpr29 side chain and the CCK8 carboxyl terminus (Lys34) introduces a restriction in the backbone conformational freedom. However, the interaction of cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 with the micelles still plays an important role in the stabilisation of the bioactive conformation. A careful comparison of the NMR structure of the cyclic peptide in a DPC micelle aqueous solution with the structure of the rationally designed model underlines that the turn-like conformation in the Trp30-Met31 region is preserved, such that the Trp30 and Met31 side chains can adopt the proper spatial orientation to interact with the CCK(A) receptor. The binding properties of cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 to the N-terminal receptor fragment have been investigated by fluorescence spectroscopy in a micellar environment. Estimates of the apparent dissociation constant, K(d), were in the range of 70-150 nM, with a mean value of 120+/-27 nM. Preliminary nuclear medicine studies on cell lines transfected with the CCK(A) receptor indicate that the sulfated-Tyr derivative of cyclo(29,34)[Dpr(29),Lys(34)]-CCK8 displaces the natural ligand with an IC(50) value of 15 microM.     

Behavior of Paramagnetic Iron during the Thermal Transformations of Kaolinite

Kaolinites with various degrees of structural order and iron content were heated and subsequently analyzed via electron paramagnetic resonance. Iron was present in two different states in the heated materials, either as dilute structural Fe³⁺ ions or in concentrated Fe³⁺ phases. During metakaolinization, the environment of dilute Fe³⁺ ions changed, following modifications of the Al³⁺ coordination, and the Fe³⁺ concentration increased. With the breakdown of metakaolinite, the diffusion of Fe³⁺ ions induced their exsolution in superparamagnetic iron-rich domains (Fe³⁺ clusters in γ-Al₂O₃ and/or Fe³⁺ oxide nanophases), which produced a decrease in the dilute Fe³⁺ concentration. The subsequent breakdown of γ-Al₂O₃ and the formation of mullite made the dilute Fe³⁺ concentration increase again, because of the incorporation of Fe³⁺ ions in the mullite structure.     

Peptide-Lipid Interactions: Experiments and Applications

The interactions between peptides and lipids are of fundamental importance in the functioning of numerous membrane-mediated cellular processes including antimicrobial peptide action, hormone-receptor interactions, drug bioavailability across the blood-brain barrier and viral fusion processes. Moreover, a major goal of modern biotechnology is obtaining new potent pharmaceutical agents whose biological action is dependent on the binding of peptides to lipid-bilayers. Several issues need to be addressed such as secondary structure, orientation, oligomerization and localization inside the membrane. At the same time, the structural effects which the peptides cause on the lipid bilayer are important for the interactions and need to be elucidated. The structural characterization of membrane active peptides in membranes is a harsh experimental challenge. It is in fact accepted that no single experimental technique can give a complete structural picture of the interaction, but rather a combination of different techniques is necessary.     

Peptide-containing aggregates as selective nanocarriers for therapeutics

New nanocarriers are obtained by assembling two amphiphilic monomers: one containing the bioactive peptide CCK8 spaced, by a polydisperse poly(ethylene glycol), from two hydrophobic tails ((C18)2PEG2000CCK8), and the other containing a chelating agent able to give stable radiolabeled indium-111 complexes linked to the same hydrophobic moiety ((C18)2DTPAGlu). The size and shape of the supramolecular aggregates were structurally characterized by dynamic light scattering, small-angle neutron scattering, and cryogenic transmission electronic microscopy. Under the experimental conditions we investigated (pH 7.4 and molar ratio between monomers 30:70), there is the presence of high polydisperse aggregates: rod-like micelles with a radius of approximately 40 A and length >700 A, open bilayer fragments with thickness approximately 65 A, and probably vesicles. The presence of the bioactive peptide well exposed on the external surface of the aggregate allows selective targeting of nanocarriers towards the cholecystokinin receptors overexpressed by the cancerous cells. In vitro binding assays and in vivo biodistribution studies by nuclear medicine experiments using indium-111 are reported. Moreover, preliminary data concerning the drug loading capability of the aggregates and their drug efficiency on the target cells is reported by using the cytotoxic drug doxorubicin. Incubation of receptor-positive and control cells with peptide-containing aggregates filled with doxorubicin shows significantly lower cell survival in receptor-expressing cells relative to the control, for samples incubated in the presence of doxorubicin.     

A New Class of 3′‐Sulfonyl BINAPHOS Ligands: Modulation of Activity and Selectivity in Asymmetric Palladium‐Catalysed Hydrophosphorylation of Styrene

Palladium‐catalysed monophosphorylation of (R)‐2,2′‐bisperfluoroalkanesulfonates of BINOL (R^F=CF₃ or C₄F₉) by a diaryl phosphinate [Ar₂P(O)H] followed by phosphine oxide reduction (Cl₃SiH) then lithium diisopropylamide‐mediated anionic thia‐Fries rearrangement furnishes enantiomerically‐pure (R)‐2′‐diarylphosphino‐2′‐hydroxy‐3′‐perfluoralkanesulfonyl‐1,1′‐binaphthalenes [(R)‐ 8ab and (R)‐ 8g–j ], which can be further diversified by Grignard reagent (RMgX)‐mediated CF₃‐displacement [→(R)‐ 8c–f ]. Coupling of (R)‐ 8a–j with (S)‐1,1′‐binaphthalene‐2,2′‐dioxychlorophosphine (S)‐ 9 generates 3′‐sulfonyl BINAPHOS ligands (R,S)‐ 10a–j in good yields (43–82%). These new ligands are of utlility in the asymmetric hydrophosphonylation of styrene ( 1 ) by 4,4,5,5‐tetramethyl‐1,3,2‐dioxaphospholane 2‐oxide ( 2 ), for which a combination of the chiral ligands with either [Pd(Cp)(allyl)] or [Pd(allyl)(MeCN)₂]⁺/NaCH(CO₂Me)₂ proves to be a convenient and active pre‐catalyst system. A combination of an electron‐rich phosphine moiety and an electron‐deficient 3′‐sulfone moiety provides the best enantioselectivity to date for this process, affording the branched 2‐phenethenephosphonate, (−)‐iso‐ 3 , in up to 74% ee with ligand (R,S)‐ 10i , where Ar=p‐anisyl and the 3′‐SO₂R group is triflone.     

FNDC5/Irisin System in Neuroinflammation and Neurodegenerative Diseases: Update and Novel Perspective

Irisin, the circulating peptide originating from fibronectin type III domain-containing protein 5 (FNDC5), is mainly expressed by muscle fibers under peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) control during exercise. In addition to several beneficial effects on health, physical activity positively affects nervous system functioning, particularly the hippocampus, resulting in amelioration of cognition impairments. Recently, FNDC5/irisin detection in hippocampal neurons and the presence of irisin in the cerebrospinal fluid opened a new intriguing chapter in irisin history. Interestingly, in the hippocampus of mice, exercise increases FNDC5 levels and upregulates brain-derived neurotrophic factor (BDNF) expression. BDNF, displaying neuroprotection and anti-inflammatory effects, is mainly produced by microglia and astrocytes. In this review, we discuss how these glial cells can morphologically and functionally switch during neuroinflammation by modulating the expression of a plethora of neuroprotective or neurotoxic factors. We also focus on studies investigating the irisin role in neurodegenerative diseases (ND). The emerging involvement of irisin as a mediator of the multiple positive effects of exercise on the brain needs further studies to better deepen this issue and the potential use in therapeutic approaches for neuroinflammation and ND.