New method for separation and determination of denatured caseins by hydrophobic interaction chromatography

A new method for the separation of denatured alpha-, beta- and kappa- caseins by hydrophobic interaction chromatography (HIC) is proposed. The method is based on an easy solubilization of commercial and real samples by 4.0 M guanidine thiocyanate (GdmSCN) and elution on a TSK-Gel(R) Phenyl-5PW column (TosoHaas) in the presence of 8.0 M urea in the mobile phase. The procedure, applied to commercial caseins and to real, raw samples (whole milk powder and fat-free yoghurt) is not expensive, it requires common high performance liquid chromatography (HPLC) instrumentation and allows the separation of caseins also in the presence of whey proteins. Quantitative results on the analysis of alpha-, beta- and kappa-caseins in real samples are also reported.     

Nonlinear analysis of elastic round rods

Summary The nonlinear theory of elastic round rods is split into a vector equation concerning the properties of finite inextensional flexural deflections and a scalar equation concerning torsional deformations. In particular, the related boundary conditions are examined for the case of a Cardan joint. The buckling configurations of a rod under tension and torsion, constrained at both ends by Cardan joints, are determined by the linearized form of the above theory and compared with previous findings about the rod with cylindrical end hinges.

---

Sommario La teoria non lineare della verga elastica rotonda è compendiata in un'equazione vettoriale che esprime le proprietà della deformata flessionale inestensionale: le associate condizioni al contorno includono le proprietà torsionali della verga. In particolare si considerano le condizioni ai limiti per deformazioni finite nel caso di vincolo con giunto cardanico. Per la verga con giunti cardanici ai due estremi, soggetta a trazione e torsione si determinano le configurazioni critiche.

---

---

Post-graduate Student, Department of Structural Engineering, Politecnico di Torino.

---

Professor emeritus, Department of Structural Engineering, Politecnico di Torino.     

Helicoidal buckling of an elastic rod

Summary Helicoidal buckling of an elastically twisted rod, subjected to axial tension, with cylindrical hinges at both ends, whose axes remain parallel while changing their distance.

---

Sommario Una verga elastica diritta, vincolata alle estremità con cerniere cilindriche parallele è soggetta a torsione e trazione. Si determinano stati elicoidali di deformazione in cui essa può inflettersi.

     

Thick aluminium nitride films deposited by room-temperature sputtering for ultrasonic applications

Materials in film form for electromechanical transduction have a number of potential applications in ultrasound. They are presently under investigation in flexural transducers for air-coupled ultrasound and underwater sonar operating at frequencies up to a few megahertz. At higher frequencies, they have the potential to be integrated with electronics for applications of ultrasound requiring high spatial resolution. However, a number of fabrication difficulties have arisen in studies of such films. These include the high temperatures required in many thick and thin film deposition processes, making them incompatible with other stages in transducer fabrication, and difficulties maintaining film quality when thin film--typically sub-1 microm--processes are extended to higher thicknesses. In this paper, we first outline a process which has allowed us to deposit aluminium nitride (AlN) films capable of electromechanical transduction at thicknesses up to more than 5 microm without substrate heating. As an ultrasonic transduction material, AlN has functional disadvantages, particularly a high acoustic velocity and weak electromechanical transduction. However, it also has a number of advantages relating to practicality of fabrication and functionality. These include the ability to be deposited on a variety of amorphous substrates, a very high Curie temperature, low permittivity, and low electrical and mechanical losses. Here, we present experimental results highlighting the transduction capabilities of AlN deposited on aluminium electrodes on glass and lithium niobate. We compare the results with those from standard simulation processes, highlighting the reasons for discrepancies and discussing the implications for incorporation of AlN into standard ultrasonic transducer design processes.     

Nuclear magnetic resonance spectra of psychotherapeutic agents. III.. Stereochemistry of 1-methyl-5-phenyl-2,3,4,5-tetrahydro-1H-1,5-benzodiazepine-2,4-diones

The stereochemistry of some 1-methyl-5-phenyl-2,3,4,5-tetrahydro-1H-1,5-benzodiazepine-2,4-diones was determined by proton magnetic resonance using the paramagnetic shift reagent tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium [Eu(fod)₃] two of these compounds, clobazam and triflubazam, are clinically used as psychotherapeutic agents. Several model structures, with intermediate stereochemistry in the range of the possible limit situations of benzocycloheptene, -cycloheptadiene or -cycloheptatriene type, are considered; LIS (3) are computer simulated on the basis of proton geometric parameters. It was found that at room temperature, these derivatives exist in only one pseudo-boat cycloheptadiene-like conformation, showing the 5-phenyl group directed pseudo-axially. This conformational preference is interpreted in terms of a balance between the steric requirements of the bulky substituent and electronic repulsion in the ring π-system.     

Sulfenic acids in the carbohydrate field. An example of straightforward access to novel multivalent thiosaccharides

[reaction: see text] Both anomers of O-protected 1-thio-D-gluco- and -D-mannopyranoses were selected to provide the substrates for developing a smooth and general methodology that gives access to anomeric glycosulfoxides. The behavior of the corresponding beta-D-galactopyran derivatives was also investigated. 2-[1-[(2,3,4,6-Tetra-O-acetyl-beta-D-glucopyranosyl)sulfinyl](1-methyl)ethyl]malonic acid diethyl esters 4 were thermolyzed in refluxing dichloromethane for generating 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranose-1-sulfenic acid (8), in the presence of 2-propynyl beta-d-glucopyranoside tetraacetate (32). The syn-addition of transient 8 onto the triple bond of 32 furnished 2-[(2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl)sulfonyl]-2-propenyl beta-d-glucopyranoside tetraacetate (34), after m-CPBA oxidation of the corresponding sulfinyl epimeric mixture 33. This synthetic pathway appears particularly attractive since it represents an example of a mild and versatile approach to thiodisaccharides of foreseeably significant biological behavior. Various carbohydrate-derived sulfenic acids, different in glycosyl moiety and sulfenic function positioning, and various alkynylated carbohydrates can be adopted as combining units in the synthesis of alkene-linked multivalent thiosaccharides.     

Multidimensional analysis of denatured milk proteins by hydrophobic interaction chromatography coupled to a dynamic surface tension detector

Multidimensional analysis of denatured milk proteins is reported using high-performance liquid chromatography (HPLC) combined with dynamic surface tension detection (DSTD). A hydrophobic interaction chromatography (HIC) column (a TSK-Gel Phenyl-5PW column, TosoBiosep), in the presence of 3.0 M guanidine hydrochloride (GdmHCl) as denaturing agent is employed as the mobile phase. Dynamic surface tension is measured through the differential pressure across the liquid-air interface of repeatedly growing and detaching drops. Continuous surface tension measurement throughout the entire drop growth (50 ms to 4 s) is achieved, for each eluting drop of 4 s length, providing insight into both the kinetic and thermodynamic behavior of molecular orientation processes at the liquid-air interface. An automated calibration procedure and data analysis method is applied with the DSTD system, which allows two unique solvents to be used, the HIC mobile phase for the sample and a second solvent (water for example) for the standard, permitting real-time dynamic surface tension data to be obtained. Three-dimensional data is obtained, with surface tension as a function of drop time first converted to surface pressure, which is plotted as a function of the chromatographic elution time axis. Experiments were initially performed using flow injection analysis (FIA) with the DSTD system for investigating commercial single standard milk proteins (alpha-lactalbumin, beta-lactoglobulin, alpha-, beta-, kappa-casein and a casein mixture) denatured by GdmHCl. These FIA-DSTD experiments allowed the separation and detection conditions to be optimized for the HIC-DSTD experiments. Thus, the HIC-DSTD system has been optimized and successfully applied to the selective analysis of surface-active casein fractions (alpha s1- and beta-casein) in a commercial casein mixture, raw milk samples (cow's, ewe's and goat's milk) and other diary products (yogurt, stracchino, mozzarella, parmesan cheese and chocolate cream). The different samples were readily distinguished based upon the selectivity provided by the HIC-DSTD method. The selectivity advantage of using DSTD relative to absorbance detection is also demonstrated.     

X-Ray Structure of an Inclusion Compound of 5,5'-Biscalix[4]arene-hexabenzoate with Toluene

The structure of the 1:3 complex between 5,5'-biscalix[4]arene-hexabenzoateand toluene has been determined by a single crystal X-ray diffraction study. Thetwo calix[4]arene subunits of the 5,5'-biscalix[4]arene system are related by aninversion center and are joined by an eclipsed biphenyl para-para linkage. Each calix[4]arene moiety displays a 1,3-alternate conformation and includes a toluene molecule within two opposite benzoate groups, while a third toluene molecule lies close to a crystallographic inversion center.     

New chromatographic method for separation and determination of denatured alphaS1-, alphaS2-, beta- and kappa-caseins by hydrophobic interaction chromatography

A procedure based on solid-phase extraction (SPE) has been developed for the simultaneous preconcentration of three widely used herbicides and seven of their most common degradation products. The compounds studied were atrazine and its metabolites, desethylatrazine, desethyldesisopropylatrazine (DEDIA), 2-hydroxyatrazine, desethyl-2-hydroxyatrazine and desisopropyl-2-hydroxyatrazine (DIHA), terbutryne and its metabolite 2-hydroxyterbutylazine, and chlorotoluron and its metabolite 3-chloro-4-methylphenylurea. A HPLC system with diode array detection was used for the separation, identification and quantification of all these analytes. In the SPE preconcentration step, different types of sorbent were studied: C₁₈ on silica and polymeric sorbents (Oasis and LiChrolut EN), the best results being obtained with the styrene–divinylbenzene cartridge and when the elution was performed with methanol and ethyl acetate. The detection limits obtained were between 0.1 μg l⁻¹ for DIHA and DEDIA and 0.02 μg l⁻¹ for the other analytes. The method used permitted the determination of these herbicides in drinking water at the concentration levels demanded by current legislation. The proposed method was used to evaluate the presence and evolution with time of these herbicides and their degradation products in samples of surface and ground waters from agricultural zones of the provinces of Salamanca and Zamora (basins of the Rivers Guareña and Almar), Spain.     

The formation and X-ray structure of 6a-trifluoromethyl-6a, 12-dihydro[3,1]benzoxazino[2,1-b][1,3]- benzoxazin-5-ones,a new heterocyclic ring system

Four representatives of the new ring system [3,1]benzoxazino[2,1-b][1,3]benzoxazine, as determined by X-ray crystallography, were prepared by reaction of N-(2-hydroxybenzyl)anthranilic acids with trifluoroacetic anhydride.