Structure-activity relationships in sweeteners. I. Nitroanilines, sulphamates, oximes, isocoumarins and dipeptides

Besides the hydrophilic AH-B moiety in sweeteners, the morehydrophobic ‘third binding sites’ play an essentialrole in inducing sweetness. The distances between these molecularfunctions seem to be very critical, but exact data are lacking.To describe stereochemical requirements more precisely, newconceptual parameters were introduced, namely , and (minimum,optimum and maximum distances between these third binding sitesand the atoms A, H and B of the AH-B moieties respectively,especially appropriate for homologous series) and the S value(shortest distance between the position of an atom and the planeformed by the atoms A, H and B of the AH-B moiety). The dimensionsof the relevant side chains of five homologous series of sweeteners– sulphamates, oximes, nitroanilines, isocoumarins anddipeptides — were determined. We calculated that the positionsof the , and parameters with regard to the AH-B moieties arelocated around two main axes forming 95? angles with the H-Baxis in the AH-B moieties for sulphamates and isocoumarins and125? angles for oximes, nitroanilines and dipeptides. The positionsof are, for all potent sweeteners, situated at 70—85%of the maximum distance of viewed from the centre of the Aatom, while for , this value was found to be 15% for oximes,25% for nitroanilines, 40% for sulphamates, 50—70% fordipeptides and 65% for isocoumarins. The results indicate thereare at least three — but a maximum of four — differentreceptor sites. They have very narrow site clefts with maximumheights of -0.6 nm.     

Structure-activity relationships in sweeteners. II. Saccharins, acesulfames, chlorosugars, tryptophans and ureas

The previously introduced conceptual parameters (, , and S)to describe the stereochemical requirements for organic compoundsto taste sweet, were now applied to another series of sweetenersand to some well-known potent substances. With the help of anadapted STERIMOL computer program, the positions of relevant,hydrophobic side chains were determined in ureas, saccharins,tryptophans, chlorosugars and acesulfame derivatives in relationto their AH-B moieties. The results obtained were compared withprevious findings for five other homologous series of sweeteners.There is evidence to suggest that 6-substituted acesulfame derivativesand saccharin employ the same receptor site. in 5-substitutedacesulfame derivatives coincides with that of sulphamates calculatedearlier. in 6-chloro-D-tryptophan was found to be at equaldistances from H and B, a position which was earlier also observedfor the methyl ester group in aspartame. In the dulcin seriesof the urea derivatives, two AH-B moieties can be distinguished:the HN-CO group gives rise to , and 's which fit in the earliercalculated nitroaniline receptor site, while for the OC-NH₂group they are located near those found for isocoumarins. Thechlorine atoms in 1' '₁6'-dichlorosucrose are located aboveand below the plane of the pyranose ring at almost the samepositions with respect to the OH groups at positions 3 and 4(in fact, two equal 's), which are supposed to form the AH-Bmoiety. The high relative sweetness values of 1',6'-dichlorosucroseand 1',4,6'-trichlorogalactosucrose are most probably due tothe fact that both sweeteners can interact with the receptorsite in two ways (as such and upside-down). It is remarkablethat the average positions belonging to sweeteners with similarAH-B moieties are located very close to each other.     

G-protein {beta}{gamma} Subunit Genes Expressed in Olfactory Receptor Neurons

The expression of genes encoding G-protein ß subunitswas investigated in isolated olfactory receptor neurons fromchannel catfish. DNA sequencing of PCR products showed thatthe ß1, ß2, 2 and 3 genes were expressedin the neurons. Western blotting showed that at least threeof these subunit proteins were expressed. This first analysisof the expression of ß genes in olfactory receptorneurons suggests that these subunits may be involved in a varietyof transduction events in these cells. Chem. Senses 22: 587–592,1997.     

Endocrine, Gonadal and Behavioral Responses of Male Crucian Carp to the Hormonal Pheromone 17{alpha},20{beta}-dihydroxy-4-pregnen-3-one

The olfactory-mediated responses to the sex hormone 17,20ß-dihydroxy-4-pregnen-3-one(17,20ß-P) were studied in spermiated and regressedmale crucian carp (Carassius carassius L). The position andspontaneous locomotor activity of single male crucian carp werecontinuously recorded in an artificial stream. 17,20ß-P(final concentration 10^–11 M) was supplied to one halfand its ethanol carrier to the other half of the test area.Milt volume and gonadotropin (GtH-II) concentration in the plasmawere also measured. The smell of 17, 20ß-P significantlyincreased both the GtH-II concentration in the plasma and thevolume of strippable milt in spermiated crucian carp. Behaviorally,the side of the test area scented with 17,20ß-P wassignificantly avoided by spermiated males. None of the describedeffects of 17,20ß-P on spermiated males were observedfor the regressed crucian carp. In view of the lack of responsefrom regressed crucian carp we suggest that the observed avoidancebehavior of 17,20ß-P by spermiated males is a relevantreaction for spawning male crucian carp. The results are wellin accordance with responses obtained in the closely relatedgoldfish and gives strong support that the wild male cruciancarp use the 17,20ß-P signal from the females to preparefor the coming spawning.     

Taste of methyl-{alpha}-D-mannopyranoside: Effects of cross adaptation and Gymnema sylvestre

Methyl--D-mannopyranoside is a glycoside with a bitter-sweettaste. Adaptation to sucrose reduces the sweetness and adaptationto quinine sulphate reduces the bitterness of methyl--Dmannopyranoside.Application of Gymnema sylvestre reduces the sweetness of methyl--D-mannopyranosidewithout reducing its bitterness. These results, predicted byprevious studies, contradict a recent hypothesis and reportby Birch and Mylvaganam. ¹Supported by NIH Grant 2-RO1-NS07873-9     

The effect of thaumatins on the chemotactic behaviour of Escherichia coli

Thaumatin, an intensely sweet-tasting protein, completely blocksthe motility of Escherichia coli at concentrations 0.01%. Thismotility is restored if the phosphate concentration in the suspensionis increased to 0.025 mol/l. Unlike native thaumatin, chemicallymodified thaumatin with one acetyl group attached to the -aminogroup of the lysine residue is a good attractant for E. colilike, e.g., L-serine. Hypotheses have been constructed to explainthe action observed for thaumatins and phosphate. It is suggestedthere might be a similarity between the chemotactic activitiesof bacteria and the sensory responses in humans.     

Sialylation of intestinal microvillar membranes in newborn, sucking and weaned pigs

Affinity cytochemistry and biochemistry revealed distinctivetemporal changes in the expression of sialylated and compositionallyrelated membrane glycoconjugates in the pig small intestinebetween birth and weaning. The expression of membrane NeuAc2,6moieties, recognized by Sambucus nigra agglutinin-1, was highin newborn pigs, declined slightly during sucking and was verylow in weaned animals. Conversely, the expression of membraneNeuAc2r3 moieties, recognized by Maackia amurensis agglutinin-2,was low at birth but higher in sucking and weaned animals. Histobloodgroup O- and A-antigen expression was first detected in a minorityof sucking pigs, but was evident in all weaned pigs examined.Lactase glycoforms were isolated from solubilized microvillarmembranes of newborn and weaned pigs. The newborn (predominantly2,6-sialylated) and weaned (predominantly 1,2-fucosylated) glycoformsexhibited similar specific activity, indicating that postnatallactase decline in the pig intestine is unrelated to temporalchanges in membrane sialylation and fucosylation. fucosylation lactase lectins intestine sialylation     

Odor thresholds of some derivatives of strawberry aldehyde

The olfactory threshold concentrations of 19 derivatives ofethyl ß-methyl-ß-phenyl-,ß-epoxypropionate(strawberry aldehyde) were determined in water solution usinguntrained panellists. In spite of their similar carbon skeletons,the compounds differed considerably in their odor thresholdvalues. The lowest and highest values were found to be 0.5 p.p.m.(0.5 parts of the odorant per 10⁶ parts of water) for ß-(bromophenyl)-,ß-epoxypropionateand 720 p.p.m. for n-octyl-,ß-epoxy propionate, respectively.     

SPLITTING OF {varepsilon}-CAPROLACTAM AND OTHER LACTAMS BY BACTERIA

-Caprolactam-utilizing bacteria split -caprolactam, -valerolactamand -butyrolactam, and produce the -amino acids correspondingto them. This activity is lost when cells are grown on 6-amino-caproicacid or ammonium adipate, and reappears when cells are incubatedwith either -caprolactam or -valerolactam as the sole majororganic nutrient. Chloramphenicol inhibits this adaptation.The enzyme splitting those lactams is one and the same. It maybe called "lactam-splitting enzyme". But attempts to demonstratethe enzymic activity in a cell-free system has not yet beensuccessful. (Received September 9, 1965; )     

Integrated likelihood functions for non-Bayesian inference

Consider a model with parameter = (, ), where is the parameterof interest, and let L(, ) denote the likelihood function. Oneapproach to likelihood inference for is to use an integratedlikelihood function, in which is eliminated from L(, ) by integratingwith respect to a density function (|). The goal of this paperis to consider the problem of selecting (|) so that the resultingintegrated likelihood function is useful for non-Bayesian likelihoodinference. The desirable properties of an integrated likelihoodfunction are analyzed and these suggest that (|) should be chosenby finding a nuisance parameter that is unrelated to and thentaking the prior density for to be independent of . Such anunrelated parameter is constructed and the resulting integratedlikelihood is shown to be closely related to the modified profilelikelihood.     

An Error in the Calibration of Xylem-water Potential against Leaf-water Potential

An error occurs in the calibration of xylem pressure potential() against leaf-water potential () when the calibration is madeusing plant material in which the water stress has been inducedartificially after excision. The impostion of water stress afterexcision affects the determination more than it affects , consequentlythe relationship between these two indices of water stress isaltered. Care should be exercised to ensure that identical proceduresare adopted during . calibrations and during susbsequent fieldmeasurements of with the pressure-chamber apparatus.     

The Meaning of Matric Potential

The commonly used equation, = P - + , which describes thepartitioning of plant water potential, , into components ofhydrostatic pressure, P, osmotic pressure, , and matric potential,, is misleading. The term , which is supposed to show the influenceof a solid phase on , is zero if a consistent definition ofpressure is used in the standard thermodynamic derivation. However,it can be usefully defined by = + _D, where _D is the osmoticpressure of the equilibrium dialysate of the system. The practicaland theoretical significance of this definition is discussed.     

Using GEFs to deorphanize odorant receptors

Odorant perception is initiated when odorants activate uniquecombinations of odorant receptors (ORs) expressed in the ciliaof olfactory sensory neurons in the nose (Buck and Axel 1991;Malnic et al. 1999). One of the greatest challenges in the olfactoryscience is to correlate ORs with their ligands (to deorphanizethe ORs). The determination of OR–ligand pairs shouldreveal how the OR family is used to generate diverse odorantperceptions (Keller et al. 2007, Menashi et al. 2007). However,these studies are complicated     

AGMATINE AND N-CARBAMYLPUTRESCINE AS INTERMEDIATES IN THE FORMATION OF NICOTINE BY TOBACCO PLANTS

Agmatine-G-³H and N-carbamylputrescine-l,4-¹⁴C were effectivelyincorporated into the nicotine of tobacco plants. This resultmay indicate a route that the pyrrolidine ring of nicotine isformed from putrescine by the following pathway: arginineagmatineN-carbamylputrescineputrescinepyrrolidinering. (Received February 7, 1966; )     

Binding and metabolism of the urinous odorant 5{alpha}-androstan-3-one in sheep olfactory mucosa

The existence of specific receptors for the urinous smellingsteroid 5-androstan-3-one has been investigated in sheep olfactorymucosa using ligand-binding methods. [16,17-³H]5-Androstan-3-one(52.5 Ci/mmol) was synthesized from the precursor 5-androst-16-cn-3-one,which was prepared by two novel methods. A specific bindingcomponent, absent from control tissues was identified. The affinityconstant was 9.6 ± 6.1 x 10⁸ M^-1 (mean ± SD) andcompetition experiments with other compounds indicate high specificity.Binding activity was localized in a high M_r tissue fractionand was distinct from 3-ketosteroid dehydrogenase and otherenzymatic activity.     

Alternative Methods of Analysing Water Potential Isotherms: Some Cautions and Clarifications: I. THE IMPACT OF NON-IDEALITY AND OF SOME EXPERIMENTAL ERRORS

In recent years alternative ways have been proposed to transformmeasurements of leaf water potential, , and relative water content,R^*, in order to derive values of osmotic pressure at full turgidityin leaves and shoots, ^o(when 0). Two types of transformationsare usually considered: 1/ versus R^* and versus 1/R^*, and linearregression is used to fit the data in the region where turgoris thought to be zero. It appears that when ^o is estimated bylinear extrapolation of 1/Psi; versus R^* then apoplastic watermight not influence the accuracy of ^o but when the versus \/R^*transformation is used apoplastic water causes an underestimateof ^o. We examine the accuracy of the estimate of ^o obtainedfrom the two transformations when there are random errors in, systematic errors in , and when the osmotic solutions arenon-ideal. The 1/ versus R^* transformation generally producesthe best estimate of ⁰ by linear extrapolation.     

Pumpkin (Cucurbita sp.) seed globulin III. Comparison of subunit structures among seed globulins of various Cucurbita species and characterization of peptide components

Various Cucurbita seed globulins showed patterns similar toone another on SDS-gel electrophoresis, and ß bandsfor unreduced globulins and , ', and ' bands for reduced ones.On gel electrophoresis in 6 M urea, reduced globulin gave twoacidic and two basic bands. These corresponded to and ' chainsand ₁ and ₂ chains, respectively, identified by two-dimensionalurea-SDS gel electrophoresis. The compositions of the and ßsubunits were proposed. (Received September 8, 1977; )     

HORMONAL REGULATION ON THE INDUCTION OF {alpha}-AMYLASE ISOZYMES IN THE EMBRYO-LESS ENDOSPERM OF BARLEY

The -amylase induced by helminthosporol and gibberellic acidin the embryo-less endosperm of barley was separated into thethree fractions, 1, 2 and 3, by DEAE-cellulose column chromatography.A maximum amount of the 2. was induced by gibberellic acid andthat of the as by helminthosporol. After rechromatography, the2 induced by gibberellic acid and the as induced by helminthosporolshowed their respective single bands in an electrophoresis agargel zymogram. On the other hand, the ai induced by helminthosporoland gibberellic acid showed three bands. Dihydrohelminthosporic acid, a derivative of helminthosporol,induced the same isozymes as helminthosporol did. (Received May 8, 1967; )     

Further characterization of the binding properties of a GalNAc specific lectin from Codium fragile subspecies tomentosoides

Previous study on the binding properties of a lectin isolatedfrom Codium fragile subspecies tomentosoides (CFT) indicatesthat this lectin recognizes the GalNAc1 sequence at both reducingand nonreducing ends. In this study, the carbohydrate specificityof CFT was further characterized by quantitative precipitin(QPA) and inhibition of lectin-enzyme binding assays. Of theglycoforms tested for QPA, all asialo-GalNAc1 containing glyco-proteinsreacted well with the lectin. Asialo hamster and ovine submandibularglycoproteins, which contain almost exclusively Tn (GalNAclSer/Thr)residues as carbohydrate side chains, and Streptococcus typeC polysaccharide completely precipitated the lectin added, whilethe GalNAcβcontaining Tamm-Horsfall Sd(a⁺) glycopro-teinand its asialo product were inactive. Among the oligo-saccharidestested for inhibiting lectin-glycoprotein interaction, GalNAc13GalNAcβ13Gal14Galβ14GIc(Fp)and Galβ13GalNAc1benzyl (T) were the best, and about 125-foldmore active than GalNAc They were about 3.3, 6.6, and 43 timesmore active than Tn containing glycopeptides, GalNAc13(LFuc12)Gal(A_h) and Galβ13GalNAc(T), respectively. From the presentand previous results, it is concluded that the combining siteof CFT is probably of a groove type that recognizes from GalNAclto pentasaccharide(Fp). The carbohydrate specificity of thislectin can be constructed and summarized in decreasing orderby lectin determinants as follows: Fp and T > Tn cluster> A_h >>I/II. carbohydrate specificities Codium fragile tomentosoides glycoprotein binding lectins