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Photochemical imprint of molecular recognition sites for phenoxynaphthacene quinone (1a) in two-dimensional monolayers assembled on Au surfaces is accomplished. The photochemical imprint of the molecular recognition sites involves several steps:  The primary step includes the assembly of the trans-phenoxynaphthacene quinone monolayer (2a), followed by the rigidification of the monolayer with long-chain alkanethiols that generates a densely packed quinone monolayer. The second process involves the photoisomerization of the monolayer to the ana-quinone state (2b), followed by the nucleophilic displacement of the quinone with butylamine. The association of 1a to the imprinted sites and the dissociation of the host substrate from the sites are followed by electrochemical means as well as by microgravimetric quartz-crystal-microbalance measurements. The binding of 1a to the imprinted recognition sites reveals selectivity, and structurally related substrates do not associate to the imprinted sites. The kinetics of association of 1a to the imprinted sites and of the dissociation of 1a from the sites is affected by the length of the rigidifying alkanethiols. As the alkanethiol is longer, the association of 1a to the sites and the dissociation of 1a from the recognition sites is slower. The slower association of 1a to perforated monolayers with a long-chain alkanethiol (C18H37SH) is attributed to the blocking of the imprinted sites by the flexible alkanethiol chains. The retardation of the dissociation of 1a from the imprinted sites rigidified by the long-chain alkanethiols is attributed to the capping of the substrate by the long-chain thiols. The selectivity of the imprinted recognition sites is attributed to a structural fit of 1a to the imprinted hydrophobic contour and the synergetic stabilization of 1a in the site by complementary H-bonds.

The aggregation of Au nanoparticles in solution is induced and influenced by cationic and oligocationic species. This solution-state aggregation bears similarities to multilayer formation on surfaces but is more facile because of the nanoparticles' intrinsic instability in solution. Aggregation is followed by transmission electron microscopy (TEM) and the appearance of features at λ = 600−900 nm in the absorbance spectrum. It is found that these features are a function of factors such as the aggregant size, charge, and concentration, and the method of mixing the components, and they can be related to aggregate morphology. It seems that there are two mechanisms that can act to cause aggregation. Multiply charged aggregants can bind nanoparticles together into dense aggregates, displaying a defined absorbance at ca. λ = 700 nm, whereas singly charged aggregants cause a slower aggregation into string-like aggregates with a less defined absorbance. Whereas multiply charged aggregants can “cross-link” the layers in a multilayer structure on a surface, singly charged aggregants cannot.

The absolute orientations of the amphiphilic molecules α-hydroxy ω-bromo alcohols BrCnH2n OH, n = 21, 22, and the alkyl hydroxy esters CmH2m+1COO(CH2)nOH, m = 14, 15, n = 10, in crystalline monolayer forms on water have been determined, the former by grazing incidence X-ray diffraction (GIXD) and the latter by sum frequency generation (SFG). The assignment was made for the alkyl hydroxy esters by establishing the polar angle between the terminal CH3−C bond and the normal to the plane of the monolayer; for the bromo alcohols the assignment was made by a determination of the two-dimensional crystal structure via X-ray structure factor calculations. The SFG results are in agreement with reported GIXD and lattice energy analyses of the alkyl hydroxy esters m = 19, n = 9, 10. These studies have further revealed the absolute orientation of the alcohol C−OH bonds at the water surface, which in turn can be correlated with the ice-nucleating behavior of the monolayers on supercooled water drops in terms of the odd and even values of n.

The packing arrangements of Langmuir films on aqueous solution of simple amphiphiles, such as fatty acids, alcohols, amides, and amino acids, are now established to near atomic resolution by the method of grazing incidence X-ray diffraction (GIXD), complemented by various spectroscopic and lattice energy computational techniques. For simple aliphatic chainlike amphiphilic molecules, it is possible to correlate the extent of two-dimensional (2-D) crystallinity of the Langmuir film with molecular interactions, in terms of the nature and length of the hydrophobic chain, the type of hydrophilic headgroup, and the binding properties thereto of solute ions and molecules from the aqueous subphase. The monolayer packing arrangements of amphiphilic molecules can be engineered for the performance of photoinduced topochemical reactions, and characterized by GIXD. Racemic mixtures of amphiphiles can also be engineered, by taking advantage of intermolecular hydrogen bonding, to undergo a spontaneous separation of the left- and right-handed molecules into 2-D chiral crystals at the air−solution interface. The geometry of binding of molecules or ions from the aqueous subphase to the hydrophilic headgroups can be pinpointed by GIXD, in favorable systems. The ordered binding of solutes to the amphiphile monolayer can lead to induced nucleation of oriented organic and inorganic crystals at the solution interface. GIXD has shown that such an induction can occur via even a partial lattice match, or by structural complementarity, sometimes involving a molecular rearrangement of the amphiphiles. It is possible from monolayer-induced crystallization to glean information on the process of nucleation and on the critical size of the nuclei. A variety of different types of crystalline multilayers, composed of water-insoluble molecules such as bolaform amphiphiles, alkanes, heterosubstituted aromatics, can be formed at the air−solution interface. The number of layers formed and their polymorphic behavior can be controlled, albeit within limits, with the use of tailor-made additives. Their structures can be determined by GIXD, thus providing data on the initial stages of 3-D crystalization. Multilayers, comprising water-insoluble and water-soluble components, assembled in situ at the solution surface leading to thin film supramolecular architectures, have been engineered. These crystals have been found to be oriented vis-à-vis the solution surface and thus amenable to characterization by GIXD and other methods.

To provide more direct information on the role played by “tailor-made” auxiliary molecules in the early stages of crystal nucleation, the interplay between clusters of polar headgroups of monolayers of the copper complexes S−Cu−S‘ and S−Cu−R‘ and water-soluble copper complexes S‘−Cu−S‘ and R‘−Cu−R‘ were investigated [where S represents enantiomerically pure (S)-palmitoyl-N^ε-lysine, and S‘ and R‘ represent chiral resolved (S) and (R) forms of alanine, serine, or valine]. The different monolayers were formed by spreading the amphiphilic (R) or (S) α-amino acid on an aqueous solution of copper acetate followed by injection of the water-soluble (S‘) or (R‘) α-amino acid into the subphase. The surface pressure−molecular area isotherms of the Langmuir monolayers of the two type of complexes (S−Cu−S‘ and S−Cu−R‘) are different, the former being substantially more expanded. The polar headgroups of the S−Cu−S‘ and of the S−Cu−R‘ monolayers transferred onto a solid support assume a trans and cis configuration, respectively, according to comparative X-ray photoelectron spectroscopy (XPS) studies with appropriate cis and trans three-dimensional (3-D) α-amino acid Cu complexes. A grazing incidence X-ray diffraction (GIXD) analysis demonstrated that the S−Cu−S‘ and S−Cu−R‘ monolayers have different 2-D crystal structures, in keeping with the XPS results. A model is presented suggesting that the water-soluble S‘−Cu−S‘ copper complexes are enantioselectively bound to the periphery of the domains of the cis S−Cu−S‘ monolayers, but not to the domains of the trans S−Cu−R‘ monolayers. By symmetry, the same principal holds for the monolayers and water soluble copper complexes of α-amino acids of the opposite handedness.

The deoxycholic acid (DCA)–water (2:3) complex crystallises in space group P41212. The DCA molecules form hydrogen‐bonded layers which contain channels filled by chains of water molecules. These water molecules are linked by hydrogen bonds with each other and with the DCA molecules on the channel walls. The channel walls are thus hydrophilic unlike the hydrophobic channel walls found in the commonly observed orthorhombic P212121inclusion complexes of DCA.

A malignant teratoid medulloepithelioma that arose from the ciliary body was found in an adult Beagle. The anterior part contained relatively well-differentiated tumor cells, cartilage, and ganglion cells. These structures were interpreted as teratoid formations derived from the embryonic anlage of the medullary epithelium. The more posterior part was highly anaplastic and invasive. A transitional area contained neural rosettes of the Flexner-Wintersteiner type. This tumor is rare in both man and animals.

A medulloepithelioma of the ciliary body in the right eye of a 1-year-old goldfish (Carassius auratus) had spindle and epithelial cells arranged either in columns or around a central lumen. Vitreous-like material was found within the tumor. A medulloepithelioma is a most unusual tumor in fish in which ocular tumors are rare.

A method for resolution of conglomerates, based on morphological differences between the enantiomorphic crystals induced by tailor-made resolved impurities is described. The relationship between the crystal structure of the affected enantiomorph and the stereochemistry of the added impurity is analysed in the systems glutamic acid. HCl, asparagine. H2O and threonine in the presence of L- or D-amino acids, and it is found that the additive binds stereoselectively at the surface of the enantiomer of the same absolute configuration, occupying the same site of the amino acid groups of the host molecule. The modified side chains perturb in a second stage the regular growth of the crystal in the directions along which the side chains of the host are hydrogen bonded.

A method is described for direct determination of absolute configuration of chiral polar crystals, based on changes in crystal habit induced by tailor-made impurities. The method embodies the assignment of the direction of the chiral substrate molecule with respect to the crystal polar axis based on differences in the hemihedral faces of the substrate crystals as grown from solution in the presence and absence of impurities. The molecular packing requirements and the choice of impurities for application of this method in lysine and trans-cinnamoyl alanine are outlined.

A Staph, aureus mutant (52A5) which is deficient in wall teichoic acid (TA) was found to be highly susceptible to lysis by leukocyte extracts (ENZ) and by myeloperoxidase (MPO) when harvested from the stationary phase of growth, On the other hand, a staphylococcus mutant, which is deficient in N-acetyl glucosamine in its TA (52A2), the parent strain SH and a protein A rich strain Cowen I, could be lysed by the leukocyte factors only when harvested from the logarithmic phase of growth.The lysis of all the bacterial strains by ENZ or by MPO was strongly inhibited by lipoteichoic acid (LTA) derived either from staphylococci or from streptococci. On the other hand, deacylated LTA, TA, LPS, cytoplasmic or cell wall components derived from streptococci had no inhibitory effect on bacteriolysis. It is concluded that TA may be important in the protection of old bacterial cells against degradation by leukocyte factors, and that LTA may be involved in the control of autolytic enzymes in staphylococci. The role of MPO in bacteriolysis is also discussed.

The structure of mixed Langmuir films of the normal alkane C32H66 with different quantities of the normal alcohol C31H63OH or the diol HO(CH2)30OH on pure water were determined in situ by applying surface-sensitive methods that include grazing incidence X-ray diffraction (GIXD) and infrared reflection−absorption spectroscopy (IRRAS) and by induced freezing of water drops. Random solid solutions were formed between the alkane and C31H63OH. On the other hand, segregation of the two components was observed in the mixed systems of the alkane and HO(CH2)30OH. These findings suggest new ways for the design of hydrophobic surfaces bearing hydrophilic sites, which may be appropriate for epitaxial ice nucleation and cloud seeding purposes.

Retardation of growth of organic crystals in the presence of additives in solution has been investigated in terms of their crystal structures and the stereochemistry of the additives. A simple correlation has been established between affected directions of growth and structure of the additive. This mecnanism has been successfully applied for monitoring, in a controlled manner, the morphology of organic crystals; this is illustrated for benzamides and benzoic acids. Furthermore, the absolute configuration of polar crystals and chiral molecules has been directly assigned. This is illustrated for the polar crystal of tr-cinnamoyl alanine, and for the molecule of threonine, through morphological changes this molecule induces in the centrosymmetric crystal of serine.

The stereoselective interactions in aqueous solution between the crystal faces of centrosymmetric (R,S) serine 1 and additives resolved and racemic threonine 2 and allothreonine 3 were studied by four independent techniques: change in crystal habit on growth, anisotropic distribution of occluded additive during the crystal growth, etch pit formation on partial dissolution and atom‐atom potential energy calculations. The effects of the two diastereomers 2 and 3 are radically different due to differences in adsorption: threonine is adsorbed on the {011} crystal faces; the (R) enantiomer is adsorbed at, and eventually occluded through the (011) and (011) crystal faces replacing an (R) serine molecule. By symmetry, (S) threonine is adsorbed and occluded through the enantiotopic (011) and (011) faces replacing (S) serine. In contrast, (R) and (S) allothreonine are both adsorbed primarily at the (100) and (100) faces. The results indicate that the serine moiety of adsorbed threonine and allothreonine assume the same conformation and position as the substrate molecule. The additive is adsorbed only at specific sites such that the Cβ‐CH3groups emerge from the crystal surface. The observed effects lead in the case of threonine, but not allothreonine, to the assignment of its absolute configuration.

The centrosymmetric monoclinic crystals of glycyl‐glycine were grown in the presence of three dipeptides (racemic and resolved Gly‐Ala, Ala‐Gly and Gly‐Leu); the presence of each yielded a different morphology. It was found by a combined theoretical and experimental study that the conformation of the guest molecule is determined by the highly stereospecific intermolecular interactions between adsorbed additive and the molecules of particular surface layers of the growing crystals. Theoretical calculations predicted the preferred conformation of the leucine side chain of Gly‐Leu consistent with the change in morphology. Occluded racemic Gly‐Leu segregates along the baxis of the single crystals of Gly‐Gly.

A new chemical mass‐spectrometric method for mapping short range order in crystalline solid‐solutions of enantiomers undergoing topochemical reactions is described. We have applied this method to assigning the microstructure of the racemic mixtures of the diacrylates 1 and 2, each one in two dimorphic modifications and which undergo topochemical (2π + 2π) photocyclodimerisation and photocyclopolymerisation. All crystalline phases are disordered with respect to the enantiomeric sec‐butyl group. While the two polymorphs of 1 and polymorph α of 2 form random solid‐solutions, polymorph β of 2 forms partially ordered crystals in which the degree of order depends on the method of crystallization. It could be established that in the latter system the degree of order across the two independent centres of inversion is measurably different. The scope and limitation of this new method are discussed.

The peripheral-type benzodiazepine receptor (PBR) is not only widely expressed throughout the body, but it is also genetically conserved from bacteria to humans. Many functions have been attributed to it, but its primary role remains a puzzle. In the current study, we stably transfected cultures of MA-10 Leydig cells with either control or 18-kDa PBR antisense knockout plasmids. The antisense knockout vector was driven by the human enkephalin promoter, which contains two cAMP response elements, such that cAMP treatment of transfected cells could superinduce 18-kDa PBR antisense RNA transcription and, hence, down-regulate endogenous 18-kDa PBR mRNA levels. Control and knockout MA-10 cell lines were then compared at the level of receptor binding, thymidine incorporation, and steroid biosynthesis. Eighteen-kilodalton PBR knockout reduced the maximal binding capacity of tritium-labeled PBR ligands, and the affinity of receptors to the ligands remained unaltered. Additionally, 24-h accumulation of progesterone was lower in the knockout cells. Exposure of the two cell types to 8-bromo-cAMP resulted in a robust increase in steroid production. However, a complex pattern of steroid accumulation was observed, in which further progestin metabolism was indicated. The later decline in accumulated progesterone as well as the synthesis of androstenedione were different in the two cell types. At the level of cell proliferation, reduction of 18-kDa PBR mRNA showed no effect. Thus, we conclude that the 18-kDa PBR may have a more important role in steroidogenesis than in proliferation in this Leydig cell line.

In the rat corpus luteum, prostaglandin F2α(PGF2α) rapidly inhibits LH-induced cyclic AMP (cAMP) production when given in vivoor to isolated corpora lutea, but not to broken-cell preparations. The suggestion that increased cytosolic calcium concentration mediates PGF2αaction was investigated in corpora lutea of pseudopregnancy induced in immature rats by administration of pregnant mare serum gonadotrophin (15 i.u.). Isolated 10-day-old corpora lutea were incubated for 90 min with LH (5 μg/ml), PGF2α(10 μmol/l) and other additions, and cAMP concentration in the tissue was estimated. The putative inhibitor of intracellular calcium release or action, 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8; 30 or 150 μmol/l), did not abolish the effect of PGF2α. Similarly ineffective was the combination of TMB-8 (150 μmol/l) and calcium-depleted medium (free ionized calcium concentration, 30 nmol/l). Calmodulin inhibitors of three different chemical structures were then tested. The phenothiazine trifluoperazine, at 300 as well as 30 μmol/l, did not interfere with the inhibitory effect of PGF2αon cAMP, while suppressing (at 300 μmol/l) progesterone secretion in LH-treated tissue. Furthermore, inhibition by PGF2αwas not impaired by pimozide, a diphenylbutylpiperidine (25 and 50 μmol/l) nor by N-(6-aminohexyl)-5-chloro-1-naphthalene sulphonamide (W-7; 15 and 45 μmol/l). In the presence of LH alone, W-7 (45 μmol/l) inhibited and TMB-8 (30 μmol/l augmented cAMP accumulation, indicating that the luteal tissue was effectively exposed to these compounds. Thus, drugs known to inhibit calcium- and calmodulin-dependent processes in a variety of tissues did not abolish the inhibitory action of PGF2αon luteal cAMP production.J. Endocr.(1987) 113,205–212

We present a study of two-dimensional (2D) crystallites of cholesterol formed at the air−water interface. Grazing-incidence X-ray diffraction (GIXD) measurements performed along the surface pressure−area isotherm revealed a transition from a monolayer to a highly crystalline rectangular phase, about two layers thick. This variation in the film thickness was confirmed by ellipsometry measurements. Films transferred onto solid support by the Langmuir−Blodgett technique were seen by atomic force microscopy (AFM) to display elongated and faceted crystallites about 10 layers thick. The effect of the phospholipid dipalmitoylphosphatidylcholine (DPPC) on the 2D crystallization of cholesterol was studied by GIXD and AFM with three cholesterol:DPPC mixtures in molar ratios 1:1, 2:1, and 5:1. The phospholipid additive reduced the crystallinity of the cholesterol in the 5:1 and 2:1 mixtures, totally suppressing it in the 1:1 mixture.

Monolayers of the long-chain alcohols on water promote nucleation of ice. In order to determine the minimum size of crystalline alcohol monolayer domains that induce ice nucleation, we reduced their size in two distinct ways. One approach encompassed embedding the pure hydrocarbon alcohol, CnH2n+1OH (n = 20, 31), into a matrix of an immiscible monolayer of perfluoro alcohol C10F21C2H4OH, which is inert as an ice nucleator. The second set of experiments involved the introduction of random defects into the monolayer crystalline domains of C29H59OH through the use of the fully miscible guest alcohol molecule, C31H63OH, as additive. By these methods we estimated that ~450 water molecules are necessary to form a stable ice cluster at the onset of induced ice nucleation at a temperature just below 0 °C.

Recent studies of crystal growth in the presence of specific additives have suggested a new approach to the generation and amplification of optical activity in initially racemic mixtures1–4. This approach is based on the observation that particular enantiomers can be selectively incorporated not only into chiral crystals5–7but also into the opposite enantiotopic faces of centrosymmetric crystals3,4,8. If one such face of a centrosymmetric crystal is blocked, therefore, enantioselective occlusion into the opposite face will remove one enantiomer preferentially from the racemic mixture. We report here that this process can take place with centrosymmetric crystals of glycine, in a way that may be of relevance to the generation of optical activity during prebiotic evolution. Glycine crystals float in solution, such that only one face is available for growth. The addition of a particular enantiomer of a hydro-phobic amino acid orientates the floating crystals in such a way that the face that occludes amino acids of the opposite chirality is exposed to the solution. Thus, a statistical fluctuation in the orientation of crystals floating in an initially racemic solution could lead to the generation and amplification of optical activity.

Model molecules, designed to simulate a chain fold, self-assemble into crystalline monolayers at the air−water interface, the structure of which has been determined, in situ, by synchrotron grazing-incidence X-ray diffraction. The two-dimensional packing arrangement in such monolayers is consistent with a structure composed of ribbons containing translationally related molecules adopting an inverted U-shape. The distance between these molecules along the ribbon is optimum for creating an additional chain fold, leading to the possibility that a polymeric molecule will undulate on the water surface.

Irradiation (λ>300 nm) of eight two‐component solid solutions of β‐arylacrylamides, prepared by melting and crystallising equimolar quantities of the amides tr‐ArCH:CHCONE where Ar=C6H5, p‐MeOC6H4, p‐ClC6H4, p‐MeC6H4, and 2‐thienyl, which appeared in the αcrystal form, gave three photoproducts for each system studied: two α‐truxillic homodimers, derived from the respective monomers, and an α‐truxillic heterodimer. No other isomers were found. Similarly, two‐component solid solutions were prepared by melting and crystallising ring‐substituted cinnamic acids (tr‐ArCH:CHCO2H, where Ar=C6H5(α‐form), p—ClC6H4(β), p‐MeC6H4(α), p‐MeOC6H4(γ), o‐ClC6H4(β) and o‐CH3C6H4(γ)) and irradiated. A solid solution of two α‐type acids (each photodimerising in the solid to α‐truxillic acid) behaved like the amides, affording two α‐truxillic homodimers and an α‐truxillic heterodimer. A solid solution of an α‐type acid with a β‐type acid (photodimerising to β‐truxinic acids) gave six photoproducts: three α‐truxillic acid dimers and three β‐truxinic acid dimers (i.e., four homodimers and two heterodimers). Irradiation of a solution of a γ‐type acid (non‐photodimerising in the solid state) with an α‐type acid afforded α‐truxillic dimers (two homodimers and one heterodimer). The above results are consistent with mutual miscibility of the two components which gives rise to mixed crystal formation and subsequent photo‐behaviour within each crystal which is characteristic of the particular lattice type. However, irradiation of the mixed crystals from p‐methoxycinnamic acid (γ‐type) and p‐chlorocinnamic acid (β‐type), which afford two α‐truxillic dimers (methoxy‐homodimer and methoxy, chloro‐heterodimer) and two β‐truxinic dimers (chloro‐homodimer and methoxy, chloro‐heterodimer) indicates that new phases, unobserved for the pure compounds, can also be generated. The new dimers were all characterised by the NMR and mass spectra of their dimethyl ester derivatives and, when possible, by conversion to known compounds.

Ultrathin gold island films evaporated on transparent substrates offer promising transducers for chemical and biological sensing in the transmission surface plasmon resonance (T-SPR) mode. In the present work, the applicability of T-SPR-based systems to biosensing is demonstrated, using a well-established biological model system. Au island films were evaporated on polystyrene slides and modified with a biotinylated monolayer via a multistep surface reaction, the latter assisted by the good adhesion of metal islands to polystyrene. The biotin-derivatized Au island film was then used as a biological recognition surface for selective sensing of avidin binding, distinguishing between specific and nonspecific binding to the substrate. Transduction of the binding event into an optical signal was achieved by T-SPR spectroscopy, using plasmon intensity measurements, rather than wavelength change, for maximal sensitivity and convenience. T-SPR spectroscopy of Au island films is shown to be an effective tool for monitoring the binding of biological molecules to receptor layers on the Au surface and a promising approach to label-free optical biosensing.