A pulsed tunable dye-laser microspectrofluorometer

Summary In this paper we describe our experimental apparatus built up with the purpose of performing optical-spectroscopy studiesin vivo on subcellular organelle. Together with the technical characteristics of the system, we report the fluorescence excitation spectrum and quantum yield of a biologically important photopigment, riboflavintetrabutyrate.

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Riassunto In questo lavoro è descritto un apparato sperimentale realizzato per effettuare studi di spettroscopia otticain vivo su organelli subcellulari. Sono riportate le caratteristiche tecniche dell'apparato ed i risultati delle misure effettuate per determinare lo spettro di eccitazione ed il rendimento quantico di fluorescenza di un fotopigmento d'interesse biologico (riboflavina tetrabutirrato).

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Реэюме В этой статье мы описываем экспериментальный прибор, построенный с целью проведения оптических спектроскопических исследований в естественных условиях на субклеточных органеллах. Сообщаются технические характеристики системы. Приводятся результаты измерений спектра возбуждений и квантового выхода флуоресценции для биологически важного фотопигмента (рибофлавинтетрабутерат).

     

Entanglement in helium

Metallic Bi₂Te₃ crystalline sheets with the room-temperature resistivity of above 10 mΩ cm were prepared and their magnetoresistive transport was measured in a field of up to 9 T. The Shubnikov de Haas oscillations were identified from the secondly-derived magnetoresistance curves. While changing the angle between the field and normal axis of the sheets, we find that the oscillation periods present a cosine dependence on the angle. This indicates a two-dimensional transport due to the surface state. The work reveals a resolvable surface contribution to the overall conduction even in a metallic topological insulator.     

Alcune osservazioni sui sottogruppi abeliani del gruppoSp(n)·Sp(1)

Sunto Si studiano i sottogruppi abeliani diSp(n)·Sp(1). Viene data una caratterizzazione dei sottogruppi abeliani G diSp(n)·Sp(1) che sono immagini di sottogruppi abeliani del rivestimento universaleSp(n)·Sp(1). In relazione all'azione diSp(n)·Sp(1) su R⁴ⁿ ≡ Qⁿ si determinano i sottogruppi abeliani G per i quali Qⁿ si decompone nella somma diretta di di n sottospazi quaternionali1-dimensionali invarianti per G. Si caratterizzano i sottogruppi abeliani massimali tra quelli del tipo Z_p × … × Z_p (p numero primo). Entrata in Redazione il 21 Luglio 1976.     

Binding of Co(II) and Cu(II) cations to chemically modified wool fibres: an IR investigation

Wool fibres were modified by treatment with tannic acid (TA) solution or by acylation with ethylenediaminetetraacetic (EDTA) dianhydride. The unmodified and modified fibres were subsequently treated with Cu²⁺ and Co²⁺ solutions, at alkaline pH, and analysed by Attenuated Total Reflectance, ATR/IR spectroscopy to evaluate the changes induced in the structure of the fibre by metal binding. The spectral changes were correlated to metal adsorption results obtained by Inductive Coupled Plasma-Atomic Emission Spectrometry (ICP-AES).

The IR results were discussed in relation to our previous findings on the metal binding mode of Bombyx mori and Tussah silk fibres; the changes observed in the spectra were explained by considering the different affinity of the fibres for the modifying reagent and the amount of the metal absorbed. More relevant spectral changes were observed upon Cu²⁺ complexation rather than Co²⁺ complexation, according to the metal absorption results. The most relevant changes were observed for the EDTA-modified wool sample treated with Cu²⁺, according to the higher affinity of wool for EDTA. The IR spectra were quantitatively evaluated by the intensity ratio between the Amide I and Amide II bands (I_AmideI/I_AmideII) and its trend as a function of metal absorption was reported.

The present investigation demonstrated that the interaction between fibre and metal and the subsequent fibre modification depend on the chemical nature of the fibre, the metal cation and the modifying reagent.     

Monooxorhenium(V) complexes with the tridentate Schiff baseN-(2-hydroxyphenyl)salicylideneimine

Summary The reactions of the tridentate Schiff base ligandN-(2-hydroxyphenyl) salicylideneimine (HOPhsalH) with oxotetrachlororhenate (IV) have been investigated. The complexes (Bu₄N)[ReOCl₃(HOPhsal)], (Bu₄N)[ReOCl₂(OPhsal)],cis- [ReOCl(MeOH)(OPhsal)],trans-[ReOCl(MeOH)(OPhsal)] (1), trans-[ReOCl(OH₂)(OPhsal)] · Et₂O (2), trans-[ReOCl(OH₂)(OPhsal)] · Me₂CO,cis-[ReOCl(PPh₃)(OPhsal)],cis-[ReOCl(PMe₂Ph)(OPhsal)](3) have been synthesized and characterized. The crystal structures of(1), (2) and(3) have been solved from three-dimensional x-ray data by Patterson and Fourier methods and refined by least-squares methods to R 0.10 for(1), 0.042 for(2) and 0.059 for(3). In all the three complexes, the ligands surrounding the rhenium atom are at the apices of a distorted octahedron, with the equatorial ONO donor atoms of the tridentate Schiff base bent away from the O_oxo and toward the loosely bound MeOH in(1), H₂O in(2) and Cl in(t3). The fourth equatorial substituent is Cl (1 and2) and PMe₂Ph(3) and the rhenium atoms lie 0.30–0.37 Å above the best plane through the four equatorial atoms, in the direction of the O_oxo. All interatomic distances and angles are normal.     

New conjunctive reagents as cross-coupling partners en route to retinoid-like polyenes

[structure: see text] New conjunctive reagents E-2 and Z-3 can be used, after transmetalation, in Negishi couplings with vinyl and aryl iodides. The subsequently unmasked terminal alkynes can be further manipulated to arrive at retinoid-like products.     

An epiisopicropodophyllin aza analogue via palladium-catalyzed pseudo-domino cyclization

A new aza analogue of epiisopicropodophyllin (the C-3 epimer of podophyllotoxin) has been synthesized exploiting two original strategic steps. Rings A/B and E are entered at an early stage via a cationic benzhydrylation process. A palladium-catalyzed pseudo-domino (Pd-PDOM) intramolecular process generates rings C/D in a single synthetic operation.     

Synthesis and crystal structure of [(Ph3P)2N] [Ni2(CO)6H]

The interstitial dihydride dianion [Ni₁₂(CO)₂₁H₂]^2? is readily converted by carbon monoxide (25°C, 1 atm) into a mixture of tetracarbonylnickel and a new colourless hydride carbonyl monoanion, which has been characterized by X-ray diffraction as [Ni₂(CO)₆H]^?.     

Labdane diterpenes from Haplopappus illinitus

A chemical study of aerial parts of Haplopappus illinitus afforded five labdane diterpenoids whose structures were elucidated by high field NMR spectroscopy and 2D techniques. Four of them are dicarboxylic acids previously reported as the corresponding dimethyl ester derivatives and the fifth is a new compound.