Nature of metal binding sites in Cu(II) complexes with histidine and related N-coordinating ligands, as studied by EXAFS

Knowledge of the complexes formed by N-coordinating ligands and Cu(II) ions is of relevance in understanding the interactions of this ion with biomolecules. Within this framework, we investigated Cu(II) complexation with mono- and polydentate ligands, such as ammonia, ethylenediamine (en), and phthalocyanine (Pc). The obtained Cu-N coordination distances were 2.02 A for [Cu(NH(3))(4)](2+), 2.01 A for [Cu(en)(2)](2+), and 1.95 A for CuPc. The shorter bond distance found for CuPc is attributed to the macrocyclic effect. In addition to the structure of the first shell, information on higher coordination shells of the chelate ligands could be extracted by EXAFS, thus allowing discrimination among the different coordination modes. This was possible due to the geometry of the complexes, where the absorbing Cu atoms are coplanar with the four N atoms forming the first coordination shell of the complex. For this reason multiple scattering contributions become relevant, thus allowing determination of higher shells. This knowledge has been used to gain information about the structure of the 1:2 complexes formed by Cu(II) ions with the amino acids histidine and glycine, both showing a high affinity for Cu(II) ions. The in-solution structure of these complexes, particularly that with histidine, is not clear yet, probably due to the various possible coordination modes. In this case the square-planar arrangements glycine-histamine and histamine-histamine as well as tetrahedral coordination modes have been considered. The obtained first-shell Cu-N coordination distance for this complex is 1.99 A. The results of the higher shells EXAFS analysis point to the fact that the predominant coordination mode is the so-called histamine-histamine one in which both histidine molecules coordinate Cu(II) cations through N atoms from the amino group and from the imidazole ring.     

Infrared near-field microscopy with the Vanderbilt free electron laser: overview and perspectives

Scanning near-field optical microscopy (SNOM) makes it routinely possible to overcome the fundamental diffraction limit of standard (far-field) microscopy. Recently, aperture-based infrared SNOM performed in the spectroscopic mode, using the Vanderbilt University free electron laser, started delivering spatially-resolved information on the distribution of chemical species and on other laterally-fluctuating properties. The practical examples presented here show the great potential of this new technique both in materials science and in life sciences.     

Conventional and modified Schwarzschild objective for EUV lithography: design relations

The design criteria of a Schwarzschild-type optical system are reviewed in relation to its use as an imaging system in an extreme ultraviolet lithography setup. Both the conventional and the modified reductor imaging configurations are considered, and the respective performances, as far as the geometrical resolution in the image plane is concerned, are compared. In this connection, a formal relation defining the modified configuration is elaborated, refining a rather naïve definition presented in an earlier work. The dependence of the geometrical resolution on the image-space numerical aperture for a given magnification is investigated in detail for both configurations. So, the advantages of the modified configuration with respect to the conventional one are clearly evidenced. The results of a semi-analytical procedure are compared with those obtained from a numerical simulation performed by an optical design program. The Schwarzschild objective based system under implementation at the ENEA Frascati Center within the context of the Italian FIRB project for EUV lithography has been used as a model. Best-fit functions accounting for the behaviour of the system parameters vs. the numerical aperture are reported; they can be a useful guide for the design of Schwarzschild objective type optical systems.     

Further comparisons between the conventional and the modified Schwarzschild objectives

The performance of the modified Schwarzschild objective configuration in comparison with the ordinary configuration is further investigated, completing the analysis presented in a previous work, which was concerned with the trend of the image-plane resolution against the numerical aperture. Here, we compare the third-order aberration coefficients in both configurations, illustrating the dependence of each coefficient on both the on-axis object position and the numerical aperture. This conveys the tolerances of the two configurations to lateral and mirrors’ axial misalignments. Also, the nonconcentric mirror configuration is considered and the relative performance confronted with that of the modified configuration. PACS 42.15.Eq; 42.82.Cr     

Direct classification of olive oils by using two types of ion mobility spectrometers

In this work, we explored the use of an Ion Mobility Spectrometry (IMS) device with an ultraviolet (UV) source, and of a Gas Chromatographic (GC) column coupled to an IM Spectrometer with a tritium source, for the discrimination of three grades of olive oil, namely: extra virgin olive oil (EVOO), olive oil (OO) and pomace olive oil (POO). The three types of oil were analyzed with both equipment combinations as coupled to a headspace system and the obtained ion mobility data were consecutively processed with various chemometric tools. The classification rate for an independent validation set was 86.1% (confidence interval at 95% [83.4%, 88.5%]) with an UV-IMS and 100% (confidence interval at 95% [87%, 100%]) using a GC-IMS system. The classification rate was improved by using a more suitable ionization source and a pre-separation step prior to the IM analysis.     

Formation of Perfluorocarbon Microemulsion by Fluorinated Polyethylene Glycol

Perfluorocarbons (PFCs) are chemically and biologically inert, highly gas‐dissolving, highly fluidic, and with low surface tension. Their unique properties have triggered various applications of these compounds in the areas such as oxygen delivery, liquid ventilation, diagnosis, and lubrication. However, PFCs are immiscible with aqueous media, hence surfactants are required to make PFCs as PFC‐in‐water or water‐in‐PFC microemulsions for practical application. In order to overcome this obstacle, one approach should be beneficial to create a PFC microemulsion system with the aid of fluorosurfactants which can drive the interfacial tension of PFC with water to a very low value. In this study, the fluorophilic moiety of fluorosurfactant is an end‐functional perfluorocarbon group (R_F). Methoxy polyethylene glycol (MPEG) was selected as the hydrophilic moiety due to its unique characteristics for versatile application. A series of high yield perfluoroalkylated MPEG surfactants were synthesized by reacting different MW of perfluoroacid chlorides (C_nF_2n+1COCl) with various low MW of amino‐MPEG by amide linkage. According to the ratios of hydrophilic to fluorophilic groups balance (HFB) for these PFC microemulsions obtained, an empirical formula was applied to calculate the HFB value which can be used to design the structure of fluorosurfactant for the preparation of PFC microemulsions. Two different types of PFC liquids, perfluorooctyl bromide (PFOB) and perfluoropolyether (PFPE), were examined for the formation of PFC microemulsions. Our results indicated that the domain of PFC microemulsion was strongly affected by not only the ratio of R_F chain length to MPEG chain length of the fluorosurfactant used but also the type of PFC studied.     

The Effect of Vicinal Difluorination on the Conformation and Potency of Histone Deacetylase Inhibitors

Histone deacetylase enzymes (HDACs) are potential targets for the treatment of cancer and other diseases, but it is challenging to design isoform-selective agents. In this work, we created new analogs of two established but non-selective HDAC inhibitors. We decorated the central linker chains of the molecules with specifically positioned fluorine atoms in order to control the molecular conformations. The fluorinated analogs were screened against a panel of 11 HDAC isoforms, and minor differences in isoform selectivity patterns were observed.     

A Synthetic Route to Human Insulin Using Isoacyl Peptides

The chemical synthesis of insulin has been a longstanding challenge, mainly because of the notorious hydrophobicity of the A chain and the complicated topology of this 51‐mer peptide hormone consisting of two chains and three disulfide bonds. Reported herein is a new synthetic route utilizing the isoacyl peptide approach to address the hydrophobicity problems. The incorporation of isoacyl dipeptide segments into both A and B chains greatly improved their preparation and purification, and the RP‐HPLC recovery of the chain ligation intermediates. The new route affords human insulin with a yield of 68 % based on the starting purified A chain and an overall yield of 24 % based on the substitution of the resin used for the preparation of A chain. To the best of our knowledge, this represents the most efficient route of human insulin chemical synthesis reported to date.     

Study of self-preionized XeCl* electron-avalanched discharges

Summary Some performances of an excimer discharge at the formative stage are calculated and compared to the experimental results obtained in a XeCl^* laser device with a pin cathode without external preionization. We present a simplified discharge model for exploring the process of the preionization generated by the coronas in the cathode pin region.