Effect of relativistic many-electron interactions on photoelectron partial wave probabilities

We obtain relative cross sections for the production of photoelectrons with specific angular momentum quantum numbers. These cross sections are obtained from the polarization analysis of the visible fluorescence of ions produced when circularly polarized vacuum ultraviolet radiation photoionizes ground state Ar. The ratio of cross sections for the production of photoelectrons with the same orbital angular momentum but different total angular momenta shows strong deviations from the statistical ratio, demonstrating the importance of relativistic interactions in many-electron photoionization dynamics.     

Single-photon interference experiment using a mechanical frequency shifter

Summary A variation of the interference experiment on the single photon has been performed. By means of a mechanical effect, we change the frequency of the photon only on one arm of a Mach-Zender interferometer. We observe the beat signals even when the intensity is so small that only one photon at a time passes through the interferometer. Our experiment gives a further proof of the classical behaviour of the electromagnetic radiation at arbitrarily small intensity, in agreement with the probabilistic interpretation of quantum mechanics.

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Riassunto è stata realizzata una variante dell'esperimento d'interferenza del singolo fotone. Variando, mediante un effetto meccanico, la frequenza del fotone soltanto in uno dei due bracci di un interferometro di Mach-Zender, si osservano segnali di battimento anche quando l'intensità è così bassa che solo un fotone per volta attraversa l'interferometro. Questo esperimento dà un'ulteriore dimostrazione del comportamento classico della radiazione elettromagnetica ad intensità arbitrariamente ppicole, in accordo con l'interpretazione probabilistica della meccanica quantistica.

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Резюме Осуществлен вариант интерференционного эксперимента с одним фотоном. С помощью механического эффекта мы изменяем частоту фотона в одном из плеч интерферометра Маха-Цендера. Мы наблюдаем сигналы биения даже в том случае, когда интенсивность настолько мала, что только один фотонодновременно проходит через интерферометр. Наш эксперимент указывает на классическое поведение электромагнитного излучения при произвольномалых интенсивностях, что согласуегся с вероятностной интерпретацией квантовой механики.

     

Biomedical and Pharmacological Uses of Fluorescein Isothiocyanate Chitosan‐Based Nanocarriers

Chitosan‐based nanocarriers (ChNCs) are considered suitable drug carriers due to their ability to encapsulate a variety of drugs and cross biological barriers to deliver the cargo to their target site. Fluorescein isothiocyanate‐labeled chitosan‐based NCs (FITC@ChNCs) are used extensively in biomedical and pharmacological applications. The main advantage of using FITC@ChNCs consists of the ability to track their fate both intra and extracellularly. This journey is strictly dependent on the physico‐chemical properties of the carrier and the cell types under investigation. Other applications make use of fluorescent ChNCs in cell labeling for the detection of disorders in vivo and controlling of living cells in situ. This review describes the use of FITC@ChNCs in the various applications with a focus on understanding their usefulness in labeled drug‐delivery systems.     

Self‐(Un)rolling Biopolymer Microstructures: Rings,Tubules, and Helical Tubules from the Same Material

We have demonstrated the facile formation of reversible and fast self‐rolling biopolymer microstructures from sandwiched active–passive, silk‐on‐silk materials. Both experimental and modeling results confirmed that the shape of individual sheets effectively controls biaxial stresses within these sheets, which can self‐roll into distinct 3D structures including microscopic rings, tubules, and helical tubules. This is a unique example of tailoring self‐rolled 3D geometries through shape design without changing the inner morphology of active bimorph biomaterials. In contrast to traditional organic‐soluble synthetic materials, we utilized a biocompatible and biodegradable biopolymer that underwent a facile aqueous layer‐by‐layer (LbL) assembly process for the fabrication of 2D films. The resulting films can undergo reversible pH‐triggered rolling/unrolling, with a variety of 3D structures forming from biopolymer structures that have identical morphology and composition.     

FPOP-LC-MS/MS Suggests Differences in Interaction Sites of Amphipols and Detergents with Outer Membrane Proteins

Amphipols are a class of novel surfactants that are capable of stabilizing the native state of membrane proteins. They have been shown to be highly effective, in some cases more so than detergent micelles, at maintaining the structural integrity of membrane proteins in solution, and have shown promise as vehicles for delivering native membrane proteins into the gas phase for structural interrogation. Here, we use fast photochemical oxidation of proteins (FPOP), which irreversibly labels the side chains of solvent-accessible residues with hydroxyl radicals generated by laser photolysis of hydrogen peroxide, to compare the solvent accessibility of the outer membrane protein OmpT when solubilized with the amphipol A8-35 or with n-dodecyl-β-maltoside (DDM) detergent micelles. Using quantitative mass spectrometry analyses, we show that fast photochemical oxidation reveals differences in the extent of solvent accessibility of residues between the A8-35 and DDM solubilized states, providing a rationale for the increased stability of membrane proteins solubilized with amphipol compared with detergent micelles, as a result of additional intermolecular contacts.

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Determination of eight polyphenols and pantothenic acid in extra‐virgin olive oil samples by a simple,fast, high‐throughput and sensitive ultra high performance liquid chromatography with tandem mass spectrometry method

A new ultra high performance liquid chromatography coupled with tandem mass spectrometry method for a fast and sensitive determination of eight polyphenols (hydroxytyrosol, catechin, epicatechin, epigallocatechin gallate, oleuropein, quercetin, rutin, tyrosol) and panthotenic acid in extra‐virgin olive oil was developed. The method does not require long sample pre‐treatment and presents the lowest limit of detection and limit of quantitation values present in literature. Inter‐ and intra‐day variability, linear dynamic range of the calibration curve, recovery and matrix effect were also determined and investigated. The method was applied to several oil samples of different type and origin. Given its accuracy, precision and rapidity, the method is characterized by an interestingly high throughput, reliability, and sensitivity.     

Biocompatible Infinite‐Coordination‐Polymer Nanoparticle–Nucleic‐Acid Conjugates for Antisense Gene Regulation

Herein, we report the synthesis of DNA‐functionalized infinite‐coordination‐polymer (ICP) nanoparticles as biocompatible gene‐regulation agents. ICP nanoparticles were synthesized from ferric nitrate and a ditopic 3‐hydroxy‐4‐pyridinone (HOPO) ligand bearing a pendant azide. Addition of Fe^III to a solution of the ligand produced nanoparticles, which were colloidally unstable in the presence of salts. Conjugation of DNA to the Fe^III–HOPO ICP particles by copper‐free click chemistry afforded colloidally stable nucleic‐acid nanoconstructs. The DNA–ICP particles, when cross‐linked through sequence‐specific hybridization, exhibited narrow, highly cooperative melting transitions consistent with dense DNA surface loading. The ability of the DNA–ICP particles to enter cells and alter protein expression was also evaluated. Our results indicate that these novel particles carry nucleic acids into mammalian cells without the need for transfection agents and are capable of efficient gene knockdown.     

Correlation functions of the one-dimensional attractive Bose gas

The zero-temperature correlation functions of the one-dimensional attractive Bose gas with a delta-function interaction are calculated analytically for any value of the interaction parameter and number of particles, directly from the integrability of the model. We point out a number of interesting features, including zero recoil energy for a large number of particles, analogous to the M?ssbauer effect.     

A General Treatment to Study Molecular Complexes Stabilized by Hydrogen‐, Halogen‐, and Carbon‐Bond Networks: Experiment and Theory of (CH2F2)n⋅⋅⋅(H2O)m

Rotational spectra of several difluoromethane–water adducts have been observed using two broadband chirped‐pulse Fourier‐transform microwave (CP‐FTMW) spectrometers. The experimental structures of (CH₂F₂)???(H₂O)₂, (CH₂F₂)₂???(H₂O), (CH₂F₂)???(H₂O)₃, and (CH₂F₂)₂???(H₂O)₂ were unambiguously identified with the aid of 18 isotopic substituted species. A subtle competition between hydrogen, halogen, and carbon bonds is observed and a detailed analysis was performed on the complex network of non‐covalent interactions which stabilize each cluster. The study shows that the combination of stabilizing contact networks is able to reinforce the interaction strength through a cooperative effect, which can lead to large stable oligomers.