N-propyl Group Research Articles

Metabolism of 2-substituted quinolines with antileishmanial activity studied in vitro with liver microsomes, hepatocytes and recombinantly expressed enzymes analyzed by LC/MS

Liver microsome and hepatocyte-mediated biotransformation of three oral antileishmanial 2-substituted quinolines were investigated. One quinoline contains an n-propyl group ( 1) and the other a propenyl chain functionalized at the γ position either by a nitrile ( 2) or an alcohol ( 3). The different isoforms of rat cytochrome P450 responsible for biotransformation of 1 were also investigated. Compounds 2 and 3 mainly reacted with glutathione, preventing further metabolism. Compound 3 however, the reaction being reversible, could be released from glutathione and take alternative reaction pathways. Microsomal incubations of 1 mainly led to hydroxylation of the side chain, involving many cytochromes, predominantly CYP2B1, CYP2A6 and CYP1A1 (at more than 80%). In contrary, minor metabolites hydroxylated on the quinoline ring involved a few cytochromes. The hydroxylated products of 1 were conjugated with glucuronic acid in rat hepatocyte incubations.

Porous xerogels with a bifunctional surface layer of the composition ≡Si(CH2)3SH/≡Si(CH2)2H3

The sol-gel method with ethanol as a solvent and fluoride ion as a catalyst was used to prepare polysiloxane xerogels containing both 3-mercaptopropyl and n-propyl groups in the surface layer. An increase in the relative amount of n-propyltriethoxysilane in the initial reaction solution was found to result in the formation of xerogels with developed porous structures, which was accompanied by an increase in the specific surface area from 370 to 550 m2/g; simultaneously, other porous structure parameters such as sorption volume and pore size exhibited a tendency to increase. Atomic-force microscopy was used to show that the xerogels synthesized comprised aggregates of mean size 30 nm. An analysis of the IR and 13C cross-polarization magic angle spinning NMR data led us to conclude that the surface layer of bifunctional xerogels contained not only 3-mercaptopropyl and n-propyl groups but also silanol groups, part of nonhydrolyzed alkoxy groups, and H-bonded water molecules. The 29Si cross-polarization magic angle spinning NMR spectra revealed the presence of structural units of the compositions T1 [(≡SiO)Si(OR’)2(CH2CH2CH3) and/or (≡SiO)Si(OR’)2(CH2)3SH, R’ = H, OCH3, or OC2H5], T2 [(≡SiO)2Si(OR’)(CH2CH2CH3) and (≡SiO)2Si(OR’)(CH2)3SH], and T3 [(≡SiO)3SiCH2CH2CH3 and (≡SiO)3Si(CH2)3SH] in the xerogels synthesized.

7-(Piperidin-1-yl)-2-propyl-4-oxa-5-thia-1,6,7a-triazaindene 5,5-dioxide, a derivative of a new ring system

The title compound, C12H18N4O3S, is the first example of a fused dicyclic hexa­hydro-4-oxa-5-thia-1,6,7a-triazaindene ring system. The structure comprises two mol­ecules in the asymmetric unit, which differ in terms of the orientation of their pendant n-propyl groups.

Spin- and phase transition in the spin crossover complex [Fe(ptz) 6](BF 4) 2 studied by nuclear inelastic scattering of synchrotron radiation and by DFT calculations

Nuclear inelastic scattering (NIS) spectra of [Fe(ptz) 6](BF 4) 2 (ptz = 1- n-propyl-tetrazole) have been measured for five phases differing in spin state and crystallographic structure. Different spectral patterns have been found for the low-spin and high-spin phases and are described in terms of normal coordinate analysis of the complex molecule. For both low-spin and high-spin phases the conversion from ordered to disordered phase results in splitting of the observed NIS bands. Packing becomes visible in the NIS spectra via coupling of the Fe–N stretching vibrations with those of the terminal n-propyl groups. The DFT-based normal coordinate analysis also reveals the character of Raman markers.

Bioinorganic chemistry aspects of the inhibition of thyroid hormone biosynthesis by anti-hyperthyroid drugs

In this paper, the synthesis and characterization of thiones and selones having N,N-disubstituted imidazole are described. Experimental and theoretical studies were performed on a number of selones, which suggest that these compounds exist as zwitterions in which the selenium atom carries a large negative charge. The structures of selones were studied in solution by 77Se NMR spectroscopy and the 77Se NMR chemical shifts for the selones show large upfield shifts in the signals, confirming the zwitterionic structure of the selones in solution. The thermal isomerization of some S- and Se-substituted methyl and benzyl imidazole derivatives to produce the thermodynamically more stable N-substituted derivatives are described. A structure–activity correlation was attempted on the inhibition of LPO-catalyzed oxidation and iodination reactions by several thiouracil compounds, which indicate that the presence of an n-propyl group in PTU is important for an efficient inhibition. In contrast to the S- and Se-substituted derivatives, the selones produced by thermal isomerization exhibited efficient inhibition, indicating the importance of reactive selone (zwitterionic) moiety in the inhibition. The inhibition data on carbimazole (CBZ) support the assumption that CBZ acts as a prodrug, requiring a conversion to methimazole (MMI) for its inhibitory action on thyroid peroxidase.

Enzyme-kinetic investigation of different sarin analogues reacting with human acetylcholinesterase and butyrylcholinesterase

The pertinent threat of using organophosphorus compound (OP)-type chemical warfare agents (nerve agents) during military conflicts and by non-state actors requires the continuous search for more effective medical countermeasures. OP inhibit acetylcholinesterase (AChE) and therefore standard treatment of respective poisoning includes AChE reactivators (oximes) in combination with antimuscarinic agents. Hereby, standard oximes, 2-PAM and obidoxime, are considered to be rather insufficient against various nerve agents. Numerous experimental oximes have been investigated in the last decades by in vitro and in vivo models. Recently, we studied the reactivating potency of several oximes with human AChE inhibited by structurally different OP and observed remarkable differences depending on the OP and oxime. In order to investigate structure–activity relationships we determined the various kinetic constants (inhibition, reactivation, aging) for a series of sarin analogues bearing a methyl, ethyl, n-propyl, n-butyl, i-propyl, i-butyl, cyclohexyl or pinacolyl group with human AChE and BChE. The rate constants for the inhibition of human erythrocyte AChE and plasma BChE by these OP ( k i), for the spontaneous dealkylation ( k a) and reactivation ( k s) of OP-inhibited AChE and BChE as well as for the oxime-induced reactivation of OP-inhibited AChE and BChE by the oximes obidoxime, 2-PAM, HI 6, HLö 7 and MMB-4 were determined. With compounds bearing a n-alkyl group the inhibition rate constant increased with chain length. A relation between chain length and spontaneous reactivation velocity was also observed. In contrast, no structure–activity dependence could be observed for the oxime-induced reactivation of AChE and BChE inhibited by the compounds tested. In general, OP-inhibited AChE and BChE were susceptible towards reactivation by oximes. HLö 7 was the most potent reactivator followed by HI 6 and obidoxime while 2-PAM and MMB-4 were rather weak reactivators. These data indicate a potential structure–activity relationship concerning inhibition and spontaneous reactivation but not for oxime-induced reactivation.

Tailoring of Horseradish Peroxidase Activity in Cationic Water-in-Oil Microemulsions

Horseradish peroxidase (HRP) in cationic water-in-oil (W/O) microemulsions has always been ignored in reverse micellar enzymology, mainly because cationic surfactants are inhibitors of enzyme peroxidase. In the present study, for the first time, we have successfully introduced the cationic W/O microemulsion as an attractive host for efficient HRP activity. To this notion, much improved activity of HRP was observed in the W/O microemulsion of cetyltrimethylammonium bromide (CTAB) with an increase in n-hexanol concentration and W0 ([water]/[surfactant]), presumably due to the increased interfacial area of the microemulsions. In support of our above observation, six surfactants were synthesized with an increased headgroup size where the methyl groups of CTAB were subsequently replaced by the n-propyl and 2-hydroxyethyl groups, respectively, to prepare mono-, di-, and tripropylated/hydroxyethylated n-hexadecylammonium bromide. The peroxidase activity enhanced with headgroup size and also followed an overall trend similar to that found in the case of CTAB. Possibly, the reduced positive charge density at the augmented interfacial area by means of increase, either in headgroup size, cosurfactant concentration, and/or W0, is not capable of inactivating HRP. Also, the larger space at the interface may facilitate easier solubilization of the enzyme and increase the local concentration of enzyme and substrate, leading to the higher activity of HRP. The best activity was obtained with surfactant N-hexadecyl-N,N,N-tripropylammonium bromide, the highest ever found in any cationic W/O microemulsions, being almost 3 times higher than that found in water. Strikingly, this observed highest activity is comparable with that observed in an anionic bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT)-based system, the best W/O microemulsions used for HRP.

Synthesis, structure, and bridge-terminal alkyl exchange kinetics of pyrazolate-bridged dialuminum complexes containing bridging n-alkyl groups

Treatment of triethylaluminum with 3,5-diphenylpyrazole in a 2:1 stoichiometry afforded the ethyl-bridged complex Et 2Al(μ-Ph 2pz)(μ-Et)AlEt 2 (79%) as a colorless crystalline solid. Treatment of tri- n-propylaluminum with 3,5-di- tert-butylpyrazole in a 2:1 stoichiometry afforded the n-propyl-bridged complex ( nPr) 2Al(μ- tBu 2pz)(μ- nPr)Al( nPr) 2 (63%) and the dimeric complex [( nPr) 2Al(μ- tBu 2pz)] 2 (3%), respectively, as colorless crystalline solids. Treatment of tri- n-propylaluminum (1 equiv.) or triisobutylaluminum (1 or 2 equiv.) with 3,5-di- tert-butylpyrazole afforded exclusively the dimeric complexes [( nPr) 2Al(μ- tBu 2pz)] 2 (68%) or [( iBu) 2Al(μ- tBu 2pz)] 2 (96%), respectively, as colorless crystalline solids. The solid state structures of Et 2Al(μ-Ph 2pz)(μ-Et)AlEt 2 and ( nPr) 2Al(μ- tBu 2pz)(μ- nPr)Al( nPr) 2 consist of 3,5-disubstituted pyrazolato ligands with a di- n-alkylalumino group bonded to each nitrogen atom. An ethyl or n-propyl group acts as a bridge between the two aluminum atoms. The kinetics of the bridge-terminal exchange was determined for the bridging n-alkyl complexes by 13C NMR spectroscopy, and afforded Δ H ‡ = 1.5 ± 0.1 kcal/mol, Δ S ‡ = −46.8 ± 39.0 cal/K mol, and Δ G ( 298 K ) ‡ = 15.4 ± 11.7 kcal / mol for Et 2Al(μ-Ph 2pz)(μ-Et)AlEt 2 and Δ H ‡ = 1.7 ± 0.1 kcal/mol, Δ S ‡ = −46.6 ± 43.4 cal/K mol, and Δ G ( 298 K ) ‡ = 15.6 ± 11.7 kcal / mol for ( nPr) 2Al(μ- tBu 2pz)(μ- nPr)Al( nPr) 2. The negative values of Δ S ‡ imply ordered transition states relative to the ground states, and rotation along the N-AlR 3 vector without aluminum–nitrogen bond cleavage is proposed.

Synthesis, Biological and Modeling Studies of 1,3‐Di‐n‐propyl‐2,4‐dioxo‐6‐methyl‐8‐(substituted) 1,2,3,4‐Tetrahydro[1,2,4]‐triazolo[3,4‐f]‐purines as Adenosine Receptor Antagonists.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Design and synthesis of 3,4-dihydro-1 H-[1]-benzothieno[2,3- c]pyran and 3,4-dihydro-1 H-pyrano[3,4- b]benzofuran derivatives as non-nucleoside inhibitors of HCV NS5B RNA dependent RNA polymerase

A novel class of HCV NS5B RNA dependent RNA polymerase inhibitors containing 3,4-dihydro-1 H-[1]-benzothieno[2,3- c]pyran and 3,4-dihydro-1 H-pyrano[3,4- b]benzofuran scaffolds were designed and synthesized. Optimization of the alkyl substituent in the pyran ring showed preference for an n-propyl group, while 5,8-disubstitution pattern is preferred for the aromatic region. Analog 19 displayed potent activity with an IC 50 of 50 nM against HCV NS5B enzyme and was selective over a panel of polymerases.

Improving Random Mutagenesis by Purification of the Oligonucleotide Variants

An oligonucleotide-based mutagenesis method is presented where, contrary to most classical mutagenic approaches, preselection of the variants is performed at the oligonucleotide level to avoid cloning of non-desired sequences. The method relies on the generation of differentially phosphate-protected oligonucleotides. Protection of the phosphates is accomplished by substoichiometric incorporation of an Fmoc-protected and n-propyl-protected trinucleotide phosphoramidite during ordinary oligonucleotide assembly. Instead of the alkali-labile beta-cyanoethyl group introduced in ordinary assembly, the trinucleotide introduces the alkali-stable n-propyl group. As a result, single mutants carry three ionic phosphates less than the wild-type sequence, double mutants carry six ionic phosphates less and so on. This difference in ionic ratio enables separation of the variants by conventional polyacrilamide gel electrophoresis. In the exemplified library described herein, two sub-populations containing mainly triple and quadruple mutants were selected out of five possible sub-populations.

Head‐Group Size or Hydrophilicity of Surfactants: The Major Regulator of Lipase Activity in Cationic Water‐in‐Oil Microemulsions

To determine the crucial role of surfactant head-group size in micellar enzymology, the activity of Chromobacterium Viscosum (CV) lipase was estimated in cationic water-in-oil (w/o) microemulsions of three different series of surfactants with varied head-group size and hydrophilicity. The different series were prepared by subsequent replacement of three methyl groups of cetyltrimethylammonium bromide (CTAB) with hydroxyethyl (1-3, series I), methoxyethyl (4-6, series II), and n-propyl (7-9, series III) groups. The hydrophilicity at the polar head was gradually reduced from series I to series III. Interestingly, the lipase activity was found to be markedly higher for series II surfactants relative to their more hydrophilic analogues in series I. Moreover, the activity remained almost comparable for complementary analogues of both series I and III, though the hydrophilicity was drastically different. Noticeably, the head-group area per surfactant is almost similar for comparable surfactants of both series I and III, but distinctly higher in case of series II surfactants. Thus the lipase activity was largely regulated by the surfactant head-group size, which plays the dominant role over the hydrophilicity. The increase in head-group size presumably allows the enzyme to attain a flexible conformation as well as increase in the local concentration of enzyme and substrate, leading to the higher efficiency of lipase. The lipase showed its best activity in the microemulsion of 6 probably because of its highest head-group size. Furthermore, the observed activity in 6 is 2-3-fold and 8-fold higher than sodium bis(2-ethyl-1-hexyl)sulfosuccinate (AOT) and CTAB-based microemulsions, respectively, and in fact highest ever in any w/o microemulsions.

Synthesis, biological and modeling studies of 1,3-di- n-propyl-2,4-dioxo-6-methyl-8-(substituted) 1,2,3,4-tetrahydro [1,2,4]-triazolo [3,4-f]-purines as adenosine receptor antagonists

A new series of potential adenosine receptor antagonists with a [1,2,4]-triazolo-[3,4-f]-purine structure bearing at the 1 and 3 position n-propyl groups have been synthesized, and their affinities at the four human adenosine receptor subtypes (A 1, A 2A, A 2B and A 3) have been evaluated. In this case the presence of n-propyl groups seems to induce potency at the A 2A and A 3 adenosine receptor subtypes as opposed to our previously reported series bearing methyl substituents at the 1 and 3 positions. In particular the non-acylated derivative 17 showed affinity at these two receptor subtypes in the micromolar range. Indeed, preliminary molecular modeling investigations according to the experimental binding data indicate a modest steric and electrostatic antagonist-receptor complementarity.

Synthesis of mesoporous silica materials functionalized with n-propyl groups

Mesoporous siliceous materials with MCM-41 and MCM-48 pore architecture were functionalized by the grafting of n-propyl groups to the silica network using two routes: post-synthesis treatment of pure silica and direct grafting by a co-condensation process. XRD, N 2 adsorption–desorption measurements and 29Si solid state NMR were used to investigate the influence of the spatial pore arrangement (hexagonal and cubic, respectively) on the functionalization procedure. Different grafting rates were observed depending on the surfactant removal procedure, the nature of the material and the grafting process.

The effect of substituents on the aggregation and gelation of azo sulphonate dyes

The aggregation and gelation of sodium 1-phenylazo-2-hydroxy-6-naphthalene sulphonate azo dyes containing fluoro, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl and tert-butyl groups in the para-position to the azo group have been compared with those containing methyl and trifluoromethyl groups. The behaviour of dyes containing a fluoro group was also studied using 19F NMR spectroscopy. Aqueous solutions of sodium 1-(4-sec-butylphenylazo)-2-hydroxy-6-naphthalene sulphonate at concentrations greater than 0.01 mol dm–3 became gelatinous, whereas the other dyes containing alkyl groups did not show this effect. Although the gelation of aqueous dye solutions of fluorinated dyes has been reported previously, it had not been noticed with dyes containing hydrocarbon chains. Aggregation constants have been determined, and the thermodynamic parameters found to be influenced by chain branching and by the number of carbon atoms present. Important information has been established about the spatial arrangement of fluorine in the aromatic ring.

Copper(II) complexes of 1,10-phenanthroline-derived ligands: Studies on DNA binding properties and nuclease activity

A series of copper(II) complexes of the type [Cu(L)] 2+, where L = N, N′–dialkyl-1,10-phenanthroline-2,9-dimethanamine and R = methyl (L1), n-propyl (L2), isopropyl (L3), sec-butyl (L4), or tert-butyl (L5) group, have been synthesized. The interaction of the complexes with DNA has been studied by DNA fiber electron paramagnetic resonance (EPR) spectroscopy, emission, viscosity and electrochemical measurements and agarose gel electrophoresis. In the X-ray crystal structure of [Cu(HL2)Cl 2]NO 3, copper(II) is coordinated to two ring nitrogens and one of the two secondary amine nitrogens of the side chains and two chloride ions as well and the coordination geometry is best described as trigonal bipyramidal distorted square based pyramidal (TBDSBP). Electronic and EPR spectral studies reveal that all the complexes in aqueous solution around pH 7 possess CuN 3O 2 rather than CuN 4O chromophore with one of the alkylamino side chain not involved in coordination. The structures of the complexes in aqueous solution around pH 7 change from distorted tetragonal to trigonal bipyramidal as the size of the alkyl group is increased. The observed changes in the physicochemical features of the complexes on binding to DNA suggest that the complexes, except [Cu(L5)] 2+, bind to DNA with partial intercalation of the derivatised phen ring in between the DNA base pairs. Electrochemical studies reveal that the complexes prefer to bind to DNA in Cu(II) rather than Cu(I) oxidation state. Interestingly, [Cu(L5)] 2+ shows the highest DNA cleavage activity among all the present copper(II) complexes suggesting that the bulky N- tert-butyl group plays an important role in modifying the coordination environment around the copper(II) center, the Cu(II)/Cu(I) redox potential and hence the formation of activated oxidant responsible for the cleavage. These results were compared with those for bis(1,10-phenanthroline)copper(II), [Cu(phen) 2] 2+.

Preparation and Pharmacological Characterization of trans-2-Amino-5(6)-fluoro-6(5)-hydroxy-1-phenyl-2,3-dihydro-1H-indenes as D2-like Dopamine Receptor Agonists

The present work reports the synthesis of trans-2-amino-5(6)-fluoro-6(5)-hydroxy-1-phenyl-2,3-dihydro-1H-indenes (4a-f, 5a-f) as a continuation of our studies to better understand the significance of the halo substituent in the trans-1-phenyl-2-aminoindane series and to extend knowledge of the monophenolic ligands of DA receptors. The affinity of the new compounds and related methoxylated precursors (10-15 and 18-23) was estimated in vitro by displacement of [(3)H]SCH23390 (for D(1)-like receptors) or [(3)H]YM-09-151-2 (for D(2)-like receptors) from homogenates of porcine striatal membranes. The results indicate that unsubstituted amines 4a, 5a, 10, and 11 are poorly effective at DA receptors. The introduction of two n-propyl groups on the nitrogen atom (compounds 14, 15, 4c, and 5c) and N-allyl-N-methyl- or N-methyl-N-propyl- substitution (compounds 20-23, 4e, 4f, 5e, 5f) increased the D(2)-like affinities and selectivity. The D(2)-like agonistic activity of selected compounds 15, 20, 21, 4e, 5c, and 5e was proved by evaluating their effects on the cyclic guanosine monophosphate (cGMP) content in rat neostriatal membranes. All tested compounds displayed a potential dopamine D(2)-like agonist profile decreasing basal levels of cGMP. The selective D(2)-like agonism of compounds 20 and 5e was proved by their effects on basal striatal adenylyl cyclase activity.

Rational Design, Synthesis, and Structure−Activity Relationships of Aryltriazoles as Novel Corticotropin-Releasing Factor-1 Receptor Antagonists

Following the discovery of the very high binding affinity of 4-anilinopyrimidines against corticotropin-releasing factor receptor-1 (CRF(1)) (e.g., 1, K(i) = 2 nM), a new series of triazoles bearing different groups has been synthesized and evaluated. The compounds were prepared by cyclizations of N-acyl-S-methylisothioureas with alkylhydrazines or by cyclizations with hydrazine followed by alkylation. While members of this series showed potent binding affinity against CRF(1) receptor, there were important differences between the different regio- (7 and 12) and stereoisomeric aryltriazoles where the R(1) or R(2) side chain in 7 has an asymmetric center. In terms of overall potency, aryltriazole analogues such as 7r bearing an N-(alpha-branched benzyl)-N-propylamino side chain were the most potent, followed by analogues such as 7a, with an N-bis(cyclopropyl)methyl-N-propylamino side chain, and analogues such as 7m, with an N-(alpha-branched aliphatic)-N-propylamino side chain. While the N-propyl group was crucial for high potency, we hypothesized that the terminal methyl mimicked the 5-methyl of pyrazolo[1,5-a]pyrimidines 3 and 4. Correlation of the low-energy conformers of compounds of type 3 and 7 generated by computational analyses was very good. The size and shape of the N-alkyl group dramatically changed the potency of the triazoles, which is in contrast to the SAR seen for bicyclic CRF(1) antagonists. In general, the S-enantiomer was much more potent than the corresponding R-isomer. Furthermore, to a limited extent in the aryltriazole series the substituent on the 5-phenyl ring changed the potency up to 9-fold. (S)-1-Methyl-3-[N-(4-fluorophenylpentyl)-N-propyl]amino-5-(2-methoxy-4-dichlorophenyl)-1H-[1,2,4]triazole [(S)-7r] showed very potent binding affinity (K(i) = 2.7 nM) to CRF(1) receptors with an IC(50) of 49 nM in a cAMP inhibition assay.

Self‐Assembly of the Octanuclear Cluster [Cu8(OH)10(NH2(CH2)2CH3)12]6+ and the One‐Dimensional N‐Propylcarbamate‐Linked Coordination Polymer {[Cu(O2CNH(CH2)2CH3)(NH2(CH2)2CH3)3](ClO4)}n

The reaction of Cu(ClO4)2.6-H2O and n-propylamine in methanol gives two high-nuclearity products of well-defined compositions. At amine concentrations greater than seven equivalents compared to copper ion concentration, the system fixes carbon dioxide from air to form the one-dimensional carbamate-bridged coordination polymer, {[Cu(mu2-O,O'-O2CNH(CH2)2CH3)(NH2(CH2)2CH3)3](ClO4)}n ({1-ClO4}n). Lower relative amine concentrations lead to the self-assembly of an octanuclear copper-amine-hydroxide cluster [Cu8(OH)10(NH2(CH2)2CH3)12]6+ (2). Both compounds exhibit unique structures: {1-ClO4}n is the first mu2-O,O'-mono-N-alkylcarbamate-linked coordination polymer and 2 is the largest copper-hydroxide-monodentate amine cluster identified to date. The crystal structures indicate that the size of the n-propyl group is probably crucial for directing the formation of these compounds. Magnetic susceptibility studies indicate very weak antiferromagnetic coupling for 1. The octanuclear cluster 2 displays slightly stronger net antiferromagnetic coupling, despite the presence of a number of Cu-O(H)-Cu angles below the value of about 97 degrees that would normally be expected to yield ferromagnetic coupling.

Bis[N-(9-anthrylmethyl)propylamino]methane

In the title compound, C37H38N2, obtained by the reaction of 9-chloro­methyl­anthracene and n-propyl­amine, two 9-an­thracene­methyl­propyl­amine moeties are linked through a methyl­ene bridge. The two anthracene ring systems, and the two n-propyl groups, each lie in opposite directions.