Excitation Dynamics in Hetero‐bichromophoric Calixarene Systems

In this work, the dynamics of electronic energy transfer (EET) in bichromophoric donor–acceptor systems, obtained by functionalizing a calix[4]arene scaffold with two dyes, was experimentally and theoretically characterized. The investigated compounds are highly versatile, due to the possibility of linking the dye molecules to the cone or partial cone structure of the calix[4]arene, which directs the two active units to the same or opposite side of the scaffold, respectively. The dynamics and efficiency of the EET process between the donor and acceptor units was investigated and discussed through a combined experimental and theoretical approach, involving ultrafast pump–probe spectroscopy and density functional theory based characterization of the energetic and spectroscopic properties of the system. Our results suggest that the external medium strongly determines the particular conformation adopted by the bichromophores, with a direct effect on the extent of excitonic coupling between the dyes and hence on the dynamics of the EET process itself.     

Advantages of synthesizing trans-1,2-cyclohexanediol in a continuous flow microreactor over a standard glass apparatus

Comparison is made between the preparation of trans-1,2-cyclohexanediol in standard glassware (conventional batch production) and in a microreactor (continuous flow production). The reaction sequence involved two exothermic steps where the standard procedure demands slow reagent addition and careful temperature control. In the microreactor, the reaction could be carried out safely with up to 3 times higher reagent concentration. Synthetic benefits were a faster reaction rate and a higher purity product free of colored impurities (a feature of the batch procedure).     

Excitation energy transfer in the photosystem II core antenna complex CP43 studied by femtosecond visible/visible and visible/mid-infrared pump probe spectroscopy

Excitation energy transfer in the Photosystem II core antenna complex CP43 has been investigated by vis/vis and vis/mid-IR pump-probe spectroscopy with the aim of understanding the relation between the dynamics of energy transfer and the structural arrangement of individual chlorophyll molecules within the protein. Energy transfer was found to occur on time scales of 250 fs, 2-4 ps, and 10-12 ps. The vis/mid-IR difference spectra show that the excitation is initially distributed over chlorophylls located in environments with different polarity, since two 9-keto C=O stretching bleachings, at 1691 and 1677 cm-1, are observable at early delay times. Positive signals in the initial difference spectra around 1750 and 1720 cm-1 indicate the presence of a charge transfer state between strongly interacting chlorophylls. We conclude, both from the spectral behavior in the visible when the annihilation processes are increased and from the vis/mid-IR data, that there are two pigments (one absorbing around 670 nm and one at 683 nm) which are not connected to the other pigments on a time scale faster than 10-20 ps. Since, in the IR, on a 10 ps time scale the population of the 1691 cm-1 mode almost disappears, while the 1677 cm-1 mode is still significantly populated, we can conclude that at least some of the red absorbing pigments are located in a polar environment, possibly forming H-bonds with the surrounding protein.     

Estrous cycle influences the expression of neuronal nitric oxide synthase in the hypothalamus and limbic system of female mice

Background  

Nitric oxide plays an important role in the regulation of male and female sexual behavior in rodents, and the expression of the nitric oxide synthase (NOS) is influenced by testosterone in the male rat, and by estrogens in the female. We have here quantitatively investigated the distribution of nNOS immunoreactive (ir) neurons in the limbic hypothalamic region of intact female mice sacrificed during different phases of estrous cycle.     

Microwave-assisted extraction of coumarin and related compounds from Melilotus officinalis (L.) Pallas as an alternative to Soxhlet and ultrasound-assisted extraction

Soxhlet extraction, ultrasound-assisted extraction (USAE) and microwaves-assisted extraction (MAE) in closed system have been investigated to determine the content of coumarin, o-coumaric and melilotic acids in flowering tops of Melilotus officinalis. The extracts were analyzed with an appropriate HPLC procedure. The reproducibility of extraction and of chromatographic analysis was proved. Taking into account the extraction yield, the cost and the time, we studied the effects of extraction variables on the yield of the above-mentioned compounds. Better results were obtained with MAE (50% v/v aqueous ethanol, two heating cycles of 5 min, 50 degrees C). On the basis of the ratio extraction yield/extraction time, we therefore propose MAE as the most efficient method.     

Metabolomic Profiling of Fresh Goji (Lycium barbarum L.) Berries from Two Cultivars Grown in Central Italy: A Multi-Methodological Approach

The metabolite profile of fresh Goji berries from two cultivars, namely Big Lifeberry (BL) and Sweet Lifeberry (SL), grown in the Lazio region (Central Italy) and harvested at two different periods, August and October, corresponding at the beginning and the end of the maturation, was characterized by means of nuclear magnetic resonance (NMR) and electrospray ionization Fourier transform ion cyclotron resonance (ESI FT-ICR MS) methodologies. Several classes of compounds such as sugars, amino acids, organic acids, fatty acids, polyphenols, and terpenes were identified and quantified in hydroalcoholic and organic Bligh-Dyer extracts. Sweet Lifeberry extracts were characterized by a higher content of sucrose with respect to the Big Lifeberry ones and high levels of amino acids (glycine, betaine, proline) were observed in SL berries harvested in October. Spectrophotometric analysis of chlorophylls and total carotenoids was also carried out, showing a decrease of carotenoids during the time. These results can be useful not only to valorize local products but also to suggest the best harvesting period to obtain a product with a chemical composition suitable for specific industrial use. Finally, preliminary studies regarding both the chemical characterization of Goji leaves generally considered a waste product, and the biological activity of Big Lifeberry berries extracts was also investigated. Goji leaves showed a chemical profile rich in healthy compounds (polyphenols, flavonoids, etc.) confirming their promising use in the supplements/nutraceutical/cosmetic field. MG63 cells treated with Big Lifeberry berries extracts showed a decrease of iNOS, COX-2, IL-6, and IL-8 expression indicating their significant biological activity.     

Ultrafast IR spectroscopy of polymeric cytosine nucleic acids reveal the long-lived species is due to a localised state

The decay pathways of UV-excited cytosine polymers are investigated using picosecond time-resolved infrared spectroscopy. Similar yields of a non-emissive (1)nπ* state are found in the single-stranded dC(30) polymer as in the dCMP monomer, but with a longer lifetime in the polymer (80 ps vs. 39 ps). A longer lifetime is also found in the d(CpC) dinucleotide. No evidence of excimer states is observed, suggesting that localised (1)nπ* excited states are the most significant intermediates present on the picosecond timescale.     

Structure Sensitivity in the Hydrodechlorination of Chlorophenols

The gas phase hydrodechlorination of methanolic and mixed methanol/water solutions of 2-chlorophenol, 2,6-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenol has been studied at 573 K over nickel/silica catalysts of varying (1.5–20.3 wt.% Ni) nickel loading. Each catalyst was 100% selective in promoting hydrodechlorination: the variation of catalytic activity and selectivity with time-on-stream is illustrated and catalyst deactivation is addressed. Dechlorination is quantified in terms of specific rate constants, phenol selectivity/yield and chlorine removal efficiencies. Increasing the nickel loading resulted in a marked increase in dechlorination efficiency while the introduction of water into the feed lowered the activity.