Search

The atomic-scale structure and chemical reactivity especially in aqueous environments of metal oxide surfaces have been studied. There has been an increase in scientific interest on chemical reactions at the metal oxide-aqueous solution interface due to their importance in a number of fields. The interface is reactive due to acid-base, ligand-exchange and redox chemistry involving protons, hydroxyl groups, aqueous metal ions and aqueous organic species.

Reproducible time-of-flight cluster static secondary ion mass spectra (ToF-SSIMS) were obtained for various standard calcium phosphate (CP) powders, which allowed for phase identification. X-ray diffraction was not able to detect signals from microscopic amounts of CP ([approximately]15 mmol [m.sup.-2]). The phases studied were [Alpha]-tricalcium phosphate [[Alpha]-[Ca.sub.3][(P[O.sub.4]).sub.2]], [Beta]-tricalcium phosphate [[Beta]-[Ca.sub.3]-[(P[O.sub.4]).sub.2]], amorphous calcium phosphate [[Ca.sub.3][(P[O.sub.4]).sub.2] [multiplied by] x[H.sub.2]O], octacalcium phosphate [[Ca.sub.8][H.sub.2][(P[O.sub.4]).sub.6][center dot][H.sub.2]O], brushite (CaHP[O.sub.4] 2[H.sub.2]O), and hydroxyapatite [[Ca.sub.10][(P[O.sub.4]).sub.6][(OH).sub.2]]. The SIMS spectra were obtained via bombardment with (CsI)[Cs.sup.+] projectiles. X-ray photoelectron spectroscopy (XPS) core levels of the P 2p, Ca 2p, and O 1s orbitals and the relative O 1s loss intensity were examined. The P[[O.sub.3].sup.-]/P[O.sub.2]- ratios from ToF-SSIMS spectra in conjunction with XPS of the CP powders showed much promise in differentiating between these phases at microscopic CP coverages on the metal oxide surface.

A procedure which unites ultrahigh vacuum surface analytical methods with an elevated pressure reactor can open new vistas of knowledge about the molecular details which explain and regulate the process of reactions at the gas/solid interface. These techniques can provide an understanding of the basic concepts of heterogeneous catalysis such as structure sensitivity and structure insensitivity. Model single-crystal catalysts and oxide-supported metal catalysts are presented and their abilities and limits are discussed in detail.

The methane reaction with single-crystal ruthenium catalysts is studied using high-resolution electron energy-loss spectroscopy, elevated-pressure microreactor and temperature-programmed desorption, revealing that methane dissociation leads to hydrocarbon intermediate formation. Methylidene, vinylidene and ethylidyne are formed on Ru(1120) surfaces. The Ru(0001) surface yields only methylidyne and vinylidene species.

The combined use of thermal desorption and high-resolution electron energy loss spectroscopies allows a detailed study of formaldehyde adsorption on an ultrathin NiO(100) film. The study shows that, at 90 K, the oxide catalyst adsorbs HCHO as discrete molecules, which also polymerize up to 270 K in thermodynamic equilibrium with the monomer. Chemisorption precedes but overlaps physisorption, with the Ni binding at HCHO's oxygen end below 220 K and at (C,O) above 250 K via pi-bonding. The results suggest that HCHO/NiO interaction is too weak to lead to catalytic decomposition.

The formation of F centers (oxygen vacancies bearing two electrons) in near-surface MgO films, not the presence of (Li+O-) centers, is directly responsible for the catalytic oxidative coupling of methane into ethane. A high-temperature kinetics study reveals that the (Li+O-) centers instead promote the formation of the F centers, which are sites of low coordination, that directly lead to methane activation. Thus, even at constant lithium concentration but higher temperatures (1000-1300 K) at which F centers form abundantly, ethane production increases tenfold.

The studies have shown that gas-phase CO pressure higher than 0.1 Torr is needed to segregate a sufficient amount of Pd to the surface of a well-annealed AuPd(100) sample to form contiguous Pd sites. The reaction kinetics has shown that the higher reaction rate is achieved on a surface with higher coverages of contiguous Pd sites.

Solution chemistry methods are used for preparing bimetallic CuPt alloy nanoparticle catalysts with controllable sized and shapes. The mixed-metal nanoparticles have displayed excellent catalytic properties for CO oxidation, with light-off temperatures that are nearly 200 K below those of conventional supported Pt catalysts.

The adsorption of NO on Pd(111) is studied from ultra-high-vacuum (UHV) conditions to 400 mbar using in situ polarization modulation infrared reflection adsorption spectroscopy (PM-IRS) and conventional IRAS techniques. The results have shown that stable NO dimeric and dinitrosyl species could be formed on Pd(111) at elevated pressure conditions, thereby emphasizing their potential role in catalysis.

A new high-coverage monomeric NO adsorption state on Pd(111) was observed and proposed to have a (3 X 3)-7NO structure, using in situ polarization modulation infrared reflection absorption spectroscopy and density functional theory calculations. The results emphasize the danger if extrapolating results from traditional surface science experiments performed under ultrahigh vacuum to elevated temperature and pressure conditions encountered in heterogeneous catalysis.

A study of the oxidation of CO to Co(sub 2) over Au clusters supported on MgO, annealed to temperatures between 900 and 1300 K prior to deposition of the Au cluster is reported. The results show that F-centers in MgO serves to anchor Au clusters and to control their charge state by partial transfer of charge from the substrate F-center to the Au cluster, thus promoting their catalytic activity.

The synthesis and characterization of TiO(sub 2)-supported PdAu bimetallic nanoparticle catalysts prepared using dendrimer-encapsulated nanoparticles (DENs) is reported. The key result is the compositional fidelity of the original bimetallic DENs, and to some extent their size, is retained in the supported catalyst and removal of the dendrimer template by calcinations at 500 degree Celsius.

High-resolution electron energy loss spectroscopy (HREELS), Auger spectroscopy (AES) and low-energy electron diffraction (LEED) were used to investigate the orientation and growth of benzene and pyridine on a well ordered Mo(112)-c(2 X 2)-[SiO]4. The origin for unusual adsorption behavior of benzene is discussed.

Infrared reflection absorption spectroscopy (IRAS) is used to study CO adsorption on Au clusters ranging in size from 1.8 to 3.1 nm, supported on TiO2. The results reveal that the adsorbed CO vibrational frequency blue, shifts slightly compared to that adsorbed on bulk Au, whereas the heats of adsorption increase sharply with decreasing cluster size, from 12.5 to 18.3 kcal/mol.

The adsorption of propene on Au(111) and Au(100) is investigated using temperature-programmed desorption (TPD) and high-resolution energy-resolution energy spectroscopy (HREELS). Energy loss spectra suggested that propene adsorbs with its molecular plane tilted slightly with respect to the surface plane.

Reply to the comments on the experiment of the adsorption of isocyanate study of catalytic CO + NO reaction on Pd(111) is presented. It is emphasized that the peak position of the band at 2256 cm(super -1) is in good agreement with the NCO asymmetric stretching band for a molecular HNCO species.

Infrared reflection absorption spectroscopy (IRAS) has been used to study CO adsorption on Au clusters ranging in size from 1.8 to 3.1 nm, supported on TiO2. The adsorbed CO vibrational frequency blue-shifts slightly (approximately 4 cm-1) compared to that adsorbed on bulk Au, whereas the heats of adsorption (-ΔHads) increase sharply with decreasing cluster size, from 12.5 to 18.3 kcal/mol. [ABSTRACT FROM AUTHOR]

Examines the in situ adsorption of carbon monoxide and nitrogen oxides on palladium model catalyst under high pressure conditions. Use of polarization-modulation infrared reflection absorption spectroscopy; Formation of isocyanate; Comparison of isocyanate group frequencies and isotope frequency shifts.

The distance between surface Pd atoms has been shown to control the catalytic formation of vinyl acetate tromethylene and acetic acid by AuPd catalysts. Here, we use the bulk alloy's thermodynamic properties, as well as the surface lattice spacing of a AuPd(100) alloy single-crystal model catalyst to control and optimize the concentration of the active site (Pd atom pairs at a specific Pd-Pd distance with Au nearest-neighbors). Scanning tunneling microscopy reveals that sample annealing has a direct effect on the surface Pd arrangements: short-range order preferentially forms Pd pairs located in the c(2 x 2) sites, which are known to be optimal for vinyl acetate synthesis. This effect could be harnessed for future industrial catalyst design. [ABSTRACT FROM AUTHOR]

The unique catalytic activity of supported Au nanoparticles has been ascribed to various effects including thickness/shape, the metal oxidation state, and support effects. Previously, we reported the synthesis of ordered Au monolayers and bilayers on TiOx, with the latter being significantly more active for CO oxidation than the former. In the present study, the electronic and chemical properties of ordered monolayer and bilayer Au films have been characterized by infrared reflection adsorption spectroscopy using CO as a probe and ultraviolet photoemission spectroscopy. The Au overlayers are found to be electron-rich and to have significantly different electronic properties compared with bulk Au. The common structural features of ordered Au bilayers and Au bilayer nanoparticles on TIO2(110) are described, and the exceptionally high catalytic activity of the Au bilayer structure related to its unique electronic properties. [ABSTRACT FROM AUTHOR]

Discusses the results of the international workshop on carbon management organized under the auspices of the United States Department of Energy Council on Chemical Sciences in Santa Fe, New Mexico held from April 30 to May 4, 1999. Hydrogen generation and carbon management; Selective functionalization of hydrocarbons; Utilization of carbon dioxide; Catalysis related to efficient engines for transportation.

This article studies the role of F-centers in catalysis by gold (Au) supported on magnesium oxide (MgO). The discovery of the extraordinary activity exhibited by small gold clusters on certain oxide supports has stimulated considerable research to address the origin of this unusual behavior. Treating MgO at temperatures within this range has been shown previously to produce an F-center concentration within the surface region that is proportional to the anneal temperature. The correlation between the change in the catalytic activity of the subsequently deposited Au clusters and the change in the concentration of F-centers in the MgO support is consistent with F-centers playing a direct role in the activation of the Au clusters.

Microscopic and spectroscopic techniques at near-atmospheric pressures have been used in recent years to investigate CO oxidation over Pt-group metals. New insights have been obtained that allow broadening of the understanding of this reaction beyond the ultrahigh vacuum regime where it is well-understood. However, new issues also have arisen that need clarification. In this paper, we review recent work in our laboratory, using polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) and reaction kinetics measurements from ultrahigh vacuum to near-atmospheric pressures. These studies reveal a continuity of this reaction with respect to pressure over Pt, Pd, and Rh; that is, Langmuir-Hinshelwood kinetics is exhibited over a wide pressure range with no apparent "pressure gap". The difference between Ru(0001) and other noble metals is well-understood with respect to higher oxygen binding energies and reduced CO inhibition. It is concluded that for all Pt-group metals the most active phase is one saturated with chemisorbed oxygen and with low CO coverages. The significance of oxide phases under most industrially relevant catalytic conditions suggested recently in the literature is not consistent with the experimental data.

Solution chemistry methods have been used to synthesize bimetallic CuPt alloy nanoparticle catalysts with controllable sizes and shapes. By variation of the relative ratios of the oleylamine and oleic acid stabilizers, solvent, and reduction rate, the nanoparticles could be tuned from approximately 2 nm spherical particles to nanorods with diameters of approximately 2.5 nm and aspect ratios tunable from 5:1 to 25:1. These mixed-metal nanoparticles show excellent catalytic properties for CO oxidation, with light-off temperatures that are nearly 200 K below those of conventional supported Pt catalysts.

It is demonstrated that gas-phase CO pressure higher than approximately 0.1 Torr is required to segregate a sufficient amount of Pd to the surface of a well-annealed AuPd(100) sample to form contiguous Pd sites. These contiguous sites are critical in dissociating O(2) for low-temperature CO oxidation, where CO chemisorbed on Au sites clearly participates in the reaction at temperatures below approximately 400 K. Measured reaction kinetics demonstrates that the higher reaction rate is achieved on a surface with higher coverages of contiguous Pd sites.

Ordered gold (Au) mono- and bilayer structures have been synthesized on a highly reduced titania surface. The Au bilayer exhibits a significantly higher catalytic activity for carbon monoxide oxidation than does the Au monolayer structure. This is the first report of Au completely wetting an oxide surface and demonstrates that ultrathin Au films on an oxide surface have exceptionally high catalytic activity, comparable to the activity observed for Au nanoparticles. This discovery is a key to understanding the nature of the active site of supported Au catalysts.

The unique catalytic activity of supported Au nanoparticles has been ascribed to various effects including thickness/shape, the metal oxidation state, and support effects. Previously, we reported the synthesis of ordered Au monolayers and bilayers on TiO(x), with the latter being significantly more active for CO oxidation than the former. In the present study, the electronic and chemical properties of ordered monolayer and bilayer Au films have been characterized by infrared reflection adsorption spectroscopy using CO as a probe and ultraviolet photoemission spectroscopy. The Au overlayers are found to be electron-rich and to have significantly different electronic properties compared with bulk Au. The common structural features of ordered Au bilayers and Au bilayer nanoparticles on TiO2(110) are described, and the exceptionally high catalytic activity of the Au bilayer structure related to its unique electronic properties.

We have used in situ polarization-modulation infrared reflection absorption spectroscopy to study the adsorption/dissociation of NO on Rh(111). While these studies have not been conclusive regarding the detailed surface structures formed during adsorption, they have provided important new information on the dissociation of NO on Rh(111). At moderate pressures (< or =10(-6) Torr) and temperatures (<275 K), a transition from 3-fold hollow to atop bonding is apparent. Data indicate that this transition is not due to the migration of the 3-fold hollow NO but rather to the adsorption of gas-phase NO that is directed toward the atop position due to the presence of NO decomposition products, particularly chemisorbed atomic O species at the hollow sites. These results indicate that NO dissociation occurs at temperatures well below the temperature previously reported. Additionally, high pressure (1 Torr) NO exposure at 300 K results in only atop NO, calling into question the surface structures previously proposed at these adsorption conditions consisting of atop and 3-fold hollow sites.

Au-Pd bimetallic model catalysts were synthesized as alloy clusters on SiO2 ultrathin films under ultrahigh vacuum (UHV) conditions. The surface composition and morphology were characterized with low energy ion scattering spectroscopy (LEIS), infrared reflection absorption spectroscopy (IRAS), and temperature programmed desorption (TPD). Relative to the bulk, the surface of the clusters is enriched in Au. With CO as a probe, IRAS and TPD were used to identify isolated Pd sites at the surface of the supported Au-Pd clusters. Ethylene adsorption and dehydrogenation show a clear structure-reactivity correlation with respect to the structure/composition of these Au-Pd model catalysts.

Pd, Au, and Pd-Au mixtures were deposited via physical vapor deposition onto a Mo(110) substrate, and the surface concentration and morphology of the Pd-Au mixtures were determined by low-energy ion scattering spectroscopy (LEISS), infrared absorption spectroscopy (IRAS), temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). Pd-Au mixtures form a stable alloy between 700 and 1000 K with substantial enrichment in Au compared to the bulk composition. Annealing a 1:1 Pd-Au mixture at 800 K leads to the formation of a surface alloy with a composition Au(0.8)Pd(0.2) where Pd is predominantly surrounded by Au. The surface concentration of this isolated Pd site can be systematically controlled by altering the bulk Pd-Au alloy concentration.

The growth of Ag on an ordered Al2O3 surface was studied by low energy ion scattering spectroscopy (LEIS), scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD). Three-dimensional (3D) growth of Ag clusters was observed with STM and LEIS, with the cluster size increasing with Ag coverage. The XPS core level binding energies and the Auger parameters indicate a weak interaction between the Ag clusters and the Al2O3 support. Final state effects are determined to be the primary contribution to the Ag core level binding energy shift. Nonzero order kinetics was observed for Ag desorption in TPD with the Ag sublimation energy decreasing with decreasing cluster size.

Infrared reflection absorption spectroscopy (IRAS) has been used to study CO-NO and CO-O(2) interactions on Cu(100) between 25 and 200 K. A strong repulsive interaction between CO and NO on Cu(100) at 25 K causes tilting of the CO molecules away from the surface normal and a blue-shift of the CO vibrational frequency. Upon warming and decomposition of the NO, the CO molecules return to a bonding position normal to the surface plane. The vibrational frequency of CO blue-shifts from 2087 to 2136 cm(-1) upon coadsorption with N and O atoms formed from NO decomposition. On the other hand, the interaction of CO with O(2) at 27 K on Cu(100) in the submonolayer regime induces a red-shift of the CO vibrational frequency. Atomic oxygen, formed on Cu(100) by dissociation of O(2) at 95 K, induces a blue-shift of the vibrational frequency of coadsorbed CO to 2116 cm(-1). The CO vibrational frequency shifts to 2091 cm(-1) when the surface is annealed to 140 K, implying a change in the adsorption geometry of the oxygen atoms on Cu(100).

The accuracy of the molecular weights Mn and polydispersities of polymer brushes, determined by stretching the grafted chains using atomic force microscopy (AFM) and measuring the contour length distribution, was evaluated as a function of grafting density sigma. Poly(N,N-dimethylacrylamide) brushes were prepared by surface initiated atom transfer radical polymerization on latex particles with sigma ranging between 0.17 and 0.0059 chains/nm2 and constant Mn. The polymer, which could be cleaved from the grafting surface by hydrolysis and characterized by gel permeation chromatography (GPC), had a Mn of 30,600 and polydispersity (PDI) of 1.35. The Mn determined by the AFM technique for the higher density brushes agreed quite well with the GPC results but was significantly underestimated for the lower sigma. At high grafting density in good solvent, the extended structure of the brush increases the probability of forming segment-tip contacts located at the chain end. When the distance between chains approached twice the radius of gyration of the polymer, the transition from brush to mushroom structure presumably enabled the formation of a larger number of segment-tip contacts having separations smaller than the contour length, which explains the discrepancy between the two methods at low sigma. The PDI was typically higher than that obtained by GPC, suggesting that sampling of chains with above average contour length occurs at a frequency that is greater than their spatial distribution., (Copyright 2004 American Chemical Society)

We have estimated the molecular weight, Mn, and polydispersity, PDI, of densely grafted poly(N-isopropylacrylamide) (PNIPAM) brushes using a novel atomic force microscopy (AFM) approach. When compression of a polymer brush induced adsorption of multiple chains to an AFM tip, the resulting decompression force profile exhibited a maximum attractive force at a separation, Lm, that decayed to zero with increasing tip-sample separation. We have found that the separation Lm approximates the average contour length, Lc, determined by gel permeation chromatography (GPC). The detection of a decaying attractive force at separations larger than Lc suggests that chains of above average length sequentially break free from the tip as they are stretched away from the grafting surface. The shape of the decompression profile in this region approximately paralleled the cumulative weight fraction of the grafted chains determined by GPC. The fraction of chains of a given molecular weight determined from a single force curve fit a log-normal distribution, having a standard deviation that provided an estimate of the PDI. We have characterized two PNIPAM brushes by this AFM technique as well as by GPC coupled to a multiangle laser light-scattering detector (MALLS). The values obtained by AFM-(1) Mn,AFM = (3.8+/-0.5) x 10(4), PDI,(AFM) = 1.3+/-0.1 and (2) Mn,AFM = (9.4+/-1.4) x 10(4), PDI,(AFM) = 1.3+/-0.1-agreed quite well with the corresponding GPC/MALLS values of (1) Mn,GPC = 4.77 x 10(4), PDI,GPC = 1.33 and (2) Mn,GPC = 9.49 x 10(4), PDI = 1.35. This technique requires only a single force curve to obtain a statistical distribution of contour lengths and provides a novel method for estimating the Mn and PDI of appropriate uniformly grafted dense polymer layers.

Using an atomic force microscope (AFM), we have investigated the interaction forces exerted by latex particles bearing densely grafted polymer brushes consisting of poly(N,N-dimethylacrylamide) (PDMA), poly(methoxyethylacrylamide) (PMEA), poly(N-isopropylacrylamide) (PNIPAM), and PMEA-b-PNIPAM in aqueous media (good solvent). The brushes were prepared by controlled surface-initiated atom transfer radical polymerization, and the hydrodynamic thicknesses were measured by dynamic light scattering. The molecular weight (Mn), grafting density (sigma), and polydispersity (PDI) of the brushes were determined by gel permeation chromatography and multiangle laser light scattering after cleaving the polymer from the latex surface by hydrolysis. Force profiles of PDMA (0.017 nm(-2) < or = sigma < or = 0.17 nm-2) and PMEA (sigma = 0.054 nm-2) brushes were purely repulsive upon compression, with forces increasing with Mn and a, as expected, due to excluded volume interactions. At a sufficiently low grafting density (sigma = 0.012 nm-2), PDMA exhibited a long-range exponentially increasing attractive force followed by repulsion upon further compression. The long-range attractive force is believed to be due to bridging between the free chain ends and the AFM tip. The PNIPAM brush exhibited a bridging force at a grafting density of 0.037 nm(-2), a value lower than the sigma needed to induce bridging in the PDMA brush. Bridging was therefore found to depend on grafting density as well as on the nature of the monomer. The grafting densities of these polymers were larger than those typically associated with bridging. Bridging interactions were used to confirm the presence of PNIPAM in a block copolymer PMEA-b-PNIPAMA brush given that the original PMEA homopolymer brush produced a purely repulsive force. The attractive force was first detected in the block copolymer brush at a separation that increased with the length of the PNIPAM block.

Three radioactive retinoid bronoacetates were synthesized as potential retinoid affinity labels for the retinol binding site of human plasma retinol-binding protein (RBP). The compounds synthesized were beta-[9-3H]ionyl bromoacetate (IBA), beta-[11-3H]ionylideneethyl bromoacetate (IEBA), and [15-3H]retinyl bromoacetate (RBA). When excess ligand was incubated with RBP for 5 h at 37 degrees C, IBA and IEBA formed nearly 1:1 molar complexes with RBP, whereas RBA bound only approximately one-third as well. Subsequent addition of retinol to the retinoid-RBP complex resulted in complete displacement of IBA and RBA from the protein, whereas a large proportion (37%) of the [3H]IEBA remained bound to the retinol binding site of RBP. For maximization of covalent bonding of IEBA to RBP, IEBA was incubated with RBP for varying lengths of time, followed, in each instance, by addition of retinol to displace noncovalently bound IEBA. The amount of IEBA remaining bound to RBP increased with increasing incubation time, reaching a maximum of about 0.66 mol/mol of RBP at 18 h. Moreover, at each time point, the binding of retinol to RBP was inhibited to an extent that was equivalent to the amount of [3H]IEBA that was not displaced from RBP by retinol. Only a very small proportion of the bound [3H]IEBA that was not displaced with retinol could be extracted from the protein with chloroform-methanol. Taken together, these several lines of evidence strongly suggest that the IEBA was bound in the retinol binding site of RBP and was attached to the protein in a covalent manner. Thus, IEBA appears to be an effective affinity label for the retinol binding site of RBP.

A correlation study of the effects of two agents, 2-methyl-2-[p-(1,2,3,4-tetrahydro-1-naphthyl)phenoxy]propionic acid (TPIA) and amiloride, on aldosterone-induced alterations in Na+ transport, lipid synthesis, and phospholipid fatty acid composition has been carried out in the toad urinary bladder. TPIA, an inhibitor of acetyl-CoA carboxylase, inhibits aldosterone-stimulated Na+ transport as well as hormone-induced lipid synthesis and the increase in weight percentage of phospholipid long-chain polyunsaturated fatty acids. Amiloride, a diuretic which blocks sodium entry into the transporting epithelium, does not alter aldosterone's effects on lipid and fatty acid metabolism but prevents the hormone-induced increase in Na+ transport. These results support the conclusion that aldosterone increases Na+ transport in the toad urinary bladder by altering membrane fatty acid metabolism and that the lipid biosynthetic events following aldosterone treatment are a primary response to the hormone and not secondary to increased Na+ transport.

The oxytocin analogue, 2-nitro-5-azidobenzoylglycyloxytocin (NAB-Gly-oxytocin), has been synthesized and purified. The analogue is a full agonist for the stimulation of osmotic water flow in the toad urinary bladder (one-half maximal activity at 3.2 X 10(-6)M). It also enhances [14C]urea permeability in this tissue. Repetitive photolysis in the presence of NAB-Gly-oxytocin (8 X 10(-6)M) results in a progressive permanent inhibition of oxytocin stimulated urea permeability but does not alter hormone induced 3H2O movement. The inhibition is dependent on the photogeneration of the aryl nitrene intermediate and is relieved by protecting the hormone receptor with excess oxytocin (10(-6)M) during the photolysis. These results suggest that the photodependent permanent inhibition of the response to oxytocin in the toad bladder is due to covalent incorporation of the photoaffinity label, NAB-Gly-oxytocin, into the hormone receptor.

Aldosterone action in the isolated toad urinary bladder has been studied by incubation of the tissue with several specifically labeled lipogenic precursors. Within 30 min after hormone addition phospholipid synthesis is stimulated; the metabolism of oleic acid is particularly enhanced. Additionally, during this time interval a phospholipid deacylation-reacylation cycle is stimulated by aldosterone.