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Ammonium bis(biureto)borate, NH4[B(biu)2] (biu = NH–(C═O)–NH–(C═O)–NH), was synthesized as a phase pure powder from urea and triethylborate in a sophisticated solvothermal process. Its crystal stru...

Tapia-Ruiz, Nuria et al., Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid–electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology., The authors gratefully acknowledge RS2E and Alistore-ERI for funding their research into Na-ion batteries. The funding received from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 646433 (NAIADES), the Swedish Research Council, the Swedish Energy Agency (#37671-1), and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS), are all gratefully acknowledged. The many fruitful discussions within ALISTORE-ERI, and especially with M Rosa Palacín, have been most valuable. P J is also grateful for the continuous support from several of the Chalmers Areas of Advance: Materials Science and Energy. Funding from the European Union’s innovation program H2020 is acknowledged: H2020-MSCA-COFUND-2016 (DOC-FAM, Grant Agreement No. 754397). A Ponrouch is grateful to the Spanish Ministry for Economy, Industry and Competitiveness Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0496).

Several alkali and alkaline earth (iso)cyanurates were synthesized by simple aqueous acid-base reactions and aqueous salt metathesis reactions, respectively, yielding nine new structure types. Single-crystals could be grown and the crystal structures of Rb[H2C3N3O3]·H2O-I, Rb[H2C3N3O3]·H2O-II, Cs[H2C3N3O3]·0.5H2O, Sr[H2C3N3O3]2·4H2O, Ba3[H2C3N3O3]2[HC3N3O3]2·4H2O, Ca[HC3N3O3]·3.5H2O, Sr[HC3N3O3]·3H2O, Sr[HC3N3O3]·2H2O, and Sr2[C3N3O3]OH were elucidated by single-crystal XRD. Rb3[H2C3N3O3]3[H3C3N3O3]·4H2O, Cs[H2C3N3O3]·0.5H2O, and Sr[HC3N3O3]·2H2O were synthesized as phase pure, crystalline powders and were further characterized by powder XRD, FT-IR spectroscopy, UV/Vis spectroscopy, and thermogravimetry. Sr[HC3N3O3]·2H2O was shown to be an air- and water-resistant, cheap and easily obtained precursor for the phase-pure synthesis of Sr3[C3N3O3]2, a promising SHG material, and Sr[NCN]. Moreover, an interesting dependence of the polymeric anion structure from its protonation degree was observed.

The rare earth borosulfates RE2[B2(SO4)6] with RE = Y, La–Nd, Sm, Eu and Tb–Lu were synthesised under solvothermal conditions starting from the metal chlorides (Pr, Nd, Eu), the metal oxides (Y, La, Ce, Sm, Tb, Dy, Er, Tm, Lu), or the metal powders (Ho, Yb). They crystallize isotypically with Gd2[B2(SO4)6] in space group C2/c (Z = 4, a = 1346.9(3)–1379.24(17) pm, b = 1136.4(3)–1158.87(14) pm, c = 1079.9(3)–1139.54(14) pm, β = 93.369(8)–93.611(4)°). The anionic structure consists of an open-branched vierer single ring {oB, 1r}[B2S2O12(SO3)4]6−, similar to the mineral eakerite (Ca2Al2Sn[Si6O18](OH)2·2H2O) which contains {oB, 1r}[Si4O12(SiO3)2]12− moieties. The fluorescence spectroscopy of the samples with RE = Ce, Eu and Tb features emissions in the deep UV, the red, and the green part of the spectrum and furthermore revealed a weak coordination behaviour of the borosulfate anion. Thermal analysis of Eu2[B2(SO4)6] showed the highest thermal stability observed for borosulfates so far; respective trends within the borosulfate family are discussed. Additionally, the compounds were characterised by magnetic measurements, vibrational and 151Eu Mosbauer spectroscopy.

NaMg[PO3S]·9H2O was obtained as single-phase crystalline powder starting from NaOH, PSCl3 and MgCl2·6H2O. At room temperature NaMg[PO3S]·9H2O crystallises in space group Cmc21 (no. 36) (a=638.58(4) pm, b=1632.31(10) pm, c=1217.16(7) pm, Z = 4; Rint = 0.032, Rσ = 0.034, R1 = 0.036, wR2 = 0.071). The data collection at 100 K reveals an ordering of the PO3S tetrahedra by undergoing a symmetry reduction to P21 (no. 4) and an according formation of twins (C1121, unconv. setting of P21, a=631.41(3) pm, b=1630.00(7) pm, c=1219.24(5) pm, γ=90.00(2)°, Z = 4; Rint = 0.115, Rσ = 0.064, R1 = 0.045, wR2 = 0.070). NaMg[PO3S]·9H2O comprises isolated PO3S tetrahedra, distorted MgO6 octahedra and trigonal NaO6 prisms. 31P NMR spectroscopy showed a chemical shift of 33.7 ppm. The vibrational spectra of NaMg[PO3S]·9H2O were recorded and the relevant bands were assigned.

The first magnesium, manganese, cobalt, nickel, and zinc borosulfates were synthesized employing solvothermal conditions starting from the superacid H[B(HSO4)4] and the respective metal powders (Mg...

Essential genomic transactions such as DNA-damage repair and DNA replication take place on single-stranded DNA (ssDNA) or require specific single-stranded/double-stranded DNA (ssDNA/dsDNA) junctions (SDSJ). A significant challenge in single-molecule studies of DNA-protein interactions using optical trapping is the design and generation of appropriate DNA templates. In contrast to dsDNA, only a limited toolbox is available for the generation of ssDNA constructs for optical tweezers experiments. Here, we present several kinds of DNA templates suitable for single-molecule experiments requiring segments of ssDNA of several kilobases in length. These different biotinylated dsDNA templates can be tethered between optically trapped microspheres and can, by the subsequent use of force-induced DNA melting, be converted into partial or complete ssDNA molecules. We systematically investigated the time scale and efficiency of force-induced melting at different ionic strengths for DNA molecules of different sequences and lengths. Furthermore, we quantified the impact of microspheres of different sizes on the lifetime of ssDNA tethers in optical tweezers experiments. Together, these experiments provide deeper insights into the variables that impact the production of ssDNA for single molecules studies and represent a starting point for further optimization of DNA templates that permit the investigation of protein binding and kinetics on ssDNA.

Mechanical stress plays a key role in many genomic processes, such as DNA replication and transcription. The ability to predict the response of double-stranded (ds) DNA to tension is a cornerstone of understanding DNA mechanics. It is widely appreciated that torsionally relaxed dsDNA exhibits a structural transition at forces of ∼65 pN, known as overstretching, whereby the contour length of the molecule increases by ∼70%. Despite extensive investigation, the structural changes occurring in DNA during overstretching are still generating considerable debate. Three mechanisms have been proposed to account for the increase in DNA contour length during overstretching: strand unpeeling, localized base-pair breaking (yielding melting bubbles), and formation of S-DNA (strand unwinding, while base pairing is maintained). Here we show, using a combination of fluorescence microscopy and optical tweezers, that all three structures can exist, uniting the often contradictory dogmas of DNA overstretching. We visualize and distinguish strand unpeeling and melting-bubble formation using an appropriate combination of fluorescently labeled proteins, whereas remaining B-form DNA is accounted for by using specific fluorescent molecular markers. Regions of S-DNA are associated with domains where fluorescent probes do not bind. We demonstrate that the balance between the three structures of overstretched DNA is governed by both DNA topology and local DNA stability. These findings enhance our knowledge of DNA mechanics and stability, which are of fundamental importance to understanding how proteins modify the physical state of DNA.

In cells, DNA is constantly twisted, bent and stretched by numerous proteins mediating genome transactions. Understanding these essential biological processes requires in-depth knowledge of how DNA complies to mechanical stress. Two important physical features of DNA, helical structure and sequence, are not incorporated in current descriptions of DNA elasticity. Here we connect well-defined force-extension measurements with a new model for DNA elasticity: the twistable worm-like chain, in which DNA is considered a helical, elastic entity that complies to tension by extending and twisting. In addition, we reveal hitherto unnoticed stick-slip dynamics during DNA overstretching at 65pN, caused by the loss of base-pairing interactions. An equilibrium thermodynamic model solely based on DNA sequence and elasticity is presented, which captures the full complexity of this transition. These results offer deep quantitative insight in the physical properties of DNA and present a new standard description of DNA mechanics. © 2011 Macmillan Publishers Limited. All rights reserved.

K4 [BS4 O15 (OH)], Ba[B2 S3 O13 ], and Gd2 [B2 S6 O24 ] were obtained by a new synthetic approach. The strategy involves initially synthesizing the complex acid H[B(HSO4 )4 ] which is subsequently reacted in an open system with anhydrous chlorides of K, Ba, and Gd to the respective borosulfates and a volatile molecule (HCl). Furthermore, protonated borosulfates should be accessible by appropriate stoichiometry of the starting materials, particularly in closed systems, which inhibit deprotonation of H[B(HSO4 )4 ] via condensation and dehydration. This approach led to the successful synthesis of the first divalent and trivalent metal borosulfates (Ba[B2 S3 O13 ] with band-silicate topology and Gd2 [B2 S6 O24 ] with cyclosilicate topology) and the first hydrogen borosulfate K4 [BS4 O15 (OH)].

A general palladium-catalyzed alkoxycarbonylation of aryl and heteroaryl bromides has been developed in the presence of bulky monodentate phosphines. Studies of the butoxycarbonylation of three model substrates revealed the advantages of di-1-adamantyl-n-butylphosphine compared to other ligands. In the presence of this catalyst system various bromoarenes provided the corresponding benzoic acid derivatives (ester, amides, acids) in excellent yield at low catalyst loadings (0.5 mol % Pd or below).

An easy to handle and stable racemization catalyst for secondary alcohols is obtained by an in situ mixture of readily available [Ru(cymene)Cl2]2 with chelating aliphatic diamines. Optimization of the reaction revealed that N,N,N′,N′-tetramethyl-1,3-propanediamine as ligand racemizes aromatic alcohols completely within 5 h. This easy to handle and stable catalytic system is combined with a lipase-catalyzed resolution to provide an efficient dynamic kinetic resolution of secondary alcohols.

Objective Ultrafiltration failure is a common problem in continuous ambulatory peritoneal dialysis. Recent work has indicated a role of enhanced expression of nitric oxide synthase (NOS) in ultrafiltration failure. However, the conditions predisposing to increased generation of NO by the peritoneum have not been studied in detail and the cell types potentially involved have not been tested individually. Design We performed experiments in human peritoneal mesothelial cells (HPMC) in culture. Amino acid-based dialysis solution (Nutrineal; Baxter Deutschland GmbH, München, Germany), L-arginine, and glucose-containing control solutions were used and we observed the effects on the HPMC. We reasoned that amino acid-based dialysis solutions containing L-arginine, the substrate of NOS, might influence mesothelial NO generation. Nitric oxide production was measured in the supernatant using the Griess reaction. We studied the effect of the combined NOS inhibitor L-NMMA and specified the isoform of NOS involved. Results In serum-free control medium, the cells exhibited baseline generation of nitrite at a rate of 5.4 ± 0.5 μmol/g protein. Addition of 6 mmol/L L-arginine to the control medium increased nitrite significantly (11.8 ± 0.66 μmol/g protein, p < 0.002), as did amino acid-based dialysis solution (15.7 ± 1.3 μmol/g protein, p < 0.002); L-NMMA caused a significant reduction of this nitrite. HPMC expressed eNOS (NOSIII) when grown in L-arginine-supplemented medium, shown by immunocytochemistry and by reverse transcriptase-polymer chain reaction. Biochemical exposure to a calcium ionophore in 1 μmol/L concentration approximately doubled the nitrite production by L-arginine-incubated cells. Conclusion Peritoneal mesothelial cells generate NO in vitro. Generation of NO increased further in response to L-arginine supplementation of the culture medium and to amino acid-containing dialysis solution. Mesothelial cells express eNOS, which was likely involved in the observed peritoneal NO generation.

Polypentapeptides (GVGVP)n which are designed in analogy to the connective tissue protein elastin are reported to transform various kinds of energy into mechanical work by the so-called ⊿Tt-mechanism in cross-linked macroscopic polypentapeptide (PPP) films. In the literature, the responsible element of conformation in such polypeptides is described as a β- spiral and the ⊿Tt effect is explained as a sudden change of macroconformation of single polypeptide molecules from an extended but not regular state below a transition temperature Tt to the β-spiral above Tt. We examined the secondary structure of the linear PPPC(GVGVP)6 in solution with DSC, CD, UV absorption, FTIR and NMR spectroscopy. The results suggest that the β-spiral is not present in the conformational structure of the PPP molecules. The antiparallel β-sheet is proposed to be the basic regular part of conformation because it agrees with all spectroscopic data. As a consequence, the elasticity of natural elastin must be considered from a new perspective.

A substantial portion of the vasodilator response elicited by bradykinin in the human forearm is unaffected by the combined inhibition of nitric oxide (NO) synthases and cyclo-oxygenases. The cytochrome P450 (CYP) 2C9 inhibitor sulphaphenazole was recently identified as a potent inhibitor of NO- and prostacyclin (PGI2)-independent relaxation in porcine coronary arteries. The aim of the present study was to determine the effect of sulphaphenazole on basal and bradykinin-induced NO/PGI2-independent changes in the forearm blood flow (FBF) of healthy subjects. Eleven healthy male volunteers participated in this placebo-controlled study. Test agents were infused into the brachial artery and FBF was measured by bilateral venous occlusion plethysmography. Sulphaphenazole (0.02–2 mg/min) alone did not affect basal blood flow. Inhibition of the NO synthases by NG-monomethyl-L-arginine (L-NMMA; 4 μmol/min) and cyclo-oxygenases by ibuprofen (1200 mg, orally) reduced FBF to 48±7% in the absence and 50±8% in the presence of sulphaphenazole (2 mg/min; P=not significant). After pretreatment with L-NMMA (16 μmol/min) and ibuprofen (1200 mg, orally), sulphaphenazole (6 mg/min) did not substantially inhibit bradykinin-induced vasodilation. We conclude that CYP2C9-derived metabolites (i) are not involved in the regulation of baseline blood flow, and (ii) do not mediate bradykinin-induced NO/PGI2-independent vasorelaxation in the human forearm. However, determining the contribution of this enzyme to regulation of blood flow in pathological conditions associated with endothelial dysfunction requires further studies.

Background Neutrophil functions in haemodialysis (HD) patients are altered by uraemia and by HD procedure. We investigated details of the neutrophil dysfunction as its nature and origin is not well understood. This is reflected by conflicting results about neutrophil phagocytosis activity and by scarce data on the neutrophil killing capability in HD patients. Methods Using a flow-cytometric test system we have measured simultaneously phagocytosis and the production of reactive oxygen species (ROS) of neutrophils and in parallel antimicrobial killing of yeast by neutrophils. 117 whole-blood samples of healthy controls and 50 pre- and 50 post-dialysis samples of HD patients, half of them with diabetes mellitus (DM), have been evaluated. We have constructed a model to account for the dependence on the stimulus-to-cell ratio and obtain means for phagocytosis and killing at different incubation times. Results (i) HD patients have significantly lower neutrophil killing (20%) than healthy controls. (ii) Dialysis improves the killing capability by 10-15%, after dialysis the killing activity remains significantly (10%) below that of the controls. (iii) The percentage of neutrophils, which exhibit phagocytosis and produce ROS, does not differ significantly between HD patients and healthy controls. (iv) Age has no significant influence on phagocytosis and killing. Conclusion The neutrophil killing capability is reduced in HD patients while the amount of neutrophils that phagocyte and produce ROS remains unchanged. Functional impairment of uraemic neutrophils is therefore mainly a result of their reduced capability to kill microorganisms intracellularly.

Cardiovascular mortality is excessive in hemodialyzed patients. Observations in atherosclerosis suggest that endothelial dysfunction and impaired nitric oxide (NO) may be involved. However, the relation of endothelial NO to its vascular effects has not been studied conclusively in uremia. Therefore, to study these questions an invasive technique was used in normotensive patients who were on hemodialysis (HD; n = 11) and in matched control subjects (n = 11). Pharmacologic agents were infused into the brachial artery to test the chain of events from NO generation to smooth muscle cell relaxation, measuring forearm blood flow by venous occlusion plethysmography. Glyceroltrinitrate (GTN 1:2.2 nmol/min; GTN 2:4.4; GTN 3:8.8), infused to establish the reaction of the vessel wall to defined doses of NO, caused a reduced response in HD patients (control subjects: 183 +/- 20 [SEM], 246 +/- 26, and 338 +/- 29%; HD patients: 161 +/- 7, 206 +/- 12, and 262 +/- 24%; baseline = 100% for each group, P: = 0.032 by ANOVA). All subsequent data were corrected for this decreased response to defined doses of NO in HD patients. L-arginine (10 mg/min), given to exclude substrate deficiency of NO synthase (NOS), caused no significant changes (control subjects: 108 +/- 4%; HD patients: 103 +/- 4%; P: = NS). Acetylcholine (ACH 1:55 nmol/min; ACH 2:110; ACH 3:220), infused to stimulate endothelial NOS, had a significantly reduced effect in HD patients (control subjects: 246 +/- 32, 340 +/- 40, and 465 +/- 52%; HD patients: 251 +/- 55, 244 +/- 36, and 318 +/- 50%; P: = 0.002). N:-monomethyl-L-arginine (LMA 1:1 micromol/min; LMA 2:2; LMA 3:4), given to block baseline NO generation, showed an enhanced response in HD patients (control subjects: 90 +/- 2, 83 +/- 2, and 74 +/- 4%; HD patients: 84 +/- 3, 73 +/- 3, and 64 +/- 4%; P: = 0.037). Vascular response to three doses of norepinephrine (60, 120, and 240 pmol/min) was comparable in both groups, which indicated similar endothelium-independent vasoconstriction. In summary, in normotensive HD patients, (1) vasodilation to defined doses of exogenous NO was reduced, (2) there was no evidence of substrate deficiency of NOS, and (3) stimulation of NOS was impaired; however, (4) baseline NO generation was increased. It is concluded that in HD patients, the NO system has a reduced capacity to regulate vascular tone and this impairment is most significant under conditions of NOS stimulation.

ment of hyponatraemia; vasopressin; vasopressin CHF, liver cirrhosis receptor antagonists tice. Its clinical relevance is related to both the symp- Spontaneous thirst and Increased Increased toms it causes and the state of cardiovascular fluid intake dysfunction it indicates. Hyponatraemic patients may suVer from lethargy, diYculty of concentration, dis- PRA, plasma renin activity; AII, angiotensin II; Aldo, (aldosterone; orientation, muscular cramps, grand mal seizures, and Et, endothelin-1; NA, noradrenaline); aincreased in relation to the even coma. It is important to know that these symp- prevailing plasma osmolality. toms are more related to the rate of decrease of serum sodium concentration than to the absolute level of a than approximately 800 ml per day) vasopressin excess hyponatraemia reached. This surprising observation is will lead to water retention. Consequently, dilution of related to the phenomenon of osmotic unloading of all fluid compartments sets in, including dilution of cells, which causes adaptation of cell volume to the intravascular compartment leading to hyponatrae- any given degree of hyponatraemia within 2-4 days. mia. When daily fluid intake is limited to approxi- Osmotic reloading will have to occur during correction mately 800 cc, however, obligatory fluid losses via of hyponatraemia. Since this will take a similar amount kidney, GI-tract, and lungs will match intake and the of time to be completed, the rate of correction of water balance will become negative. Physicians often hyponatraemia should not be in excess of 0.5 mmol/l/h. approach hyponatraemia as if it was a primary disorder If chronic hyponatraemia is corrected too fast, i.e. at of sodium deficiency. A vast body of published obser- a rate exceeding 0.5 mmol/l/h, and if it reaches hyper- vations documents that this is an erroneous interpreta- natraemic levels, the patient will be at risk of brain tion. Hyponatraemia is almost always a condition of damage. In the literature, the occurrence of central water excess. Therefore the above interpretation may pontine myelinolysis has been well documented in such lead to deleterious therapeutic measures. circumstances. The causes of the non-osmotic vasopressin release in hyponatraemia have been studied intensively. In pre-renal hyponatraemia it was found that barorecep- Pathophysiological significance of hyponatraemia tor activation in the large central arteries is the culprit. The low arterial blood pressure typically present in the Hyponatraemia is encountered in the advanced stages advanced stages of heart failure, liver cirrhosis and of congestive heart failure (CHF ), liver cirrhosis, and volume contraction provides the stimulus to such baro- volume contraction ('prerenal pattern') as well as in receptor activation. In SIADH-type hyponatraemia, the syndrome of inappropriate antidiuretic hormone the stimuli of non-osmotic vasopressin release are not secretion ('SIADH-pattern', Table 1). Hyponatraemia precisely known. These may originate either from is a disorder of vasopressin excess, caused by non- tumour cells or from the hypothalamus. osmotic vasopressin release. Vasopressin increases water reabsorption by the kidney. When such patients Significance of hydro-osmotic V2-vasopressin drink higher than minimal amounts of water (more receptors

The laser control of reactions in solution has recently been a topic of growing interest. The theoretical possibility for such control has now been established. This paper investigates two closely related issues regarding potential practical implementation of condensed phase control schemes. A previous study from our group was able to demonstrate control assuming that a laser field coupled only to a reaction coordinate. The assumption that the laser will not couple to the condensed phase environment is a drastic simplification, and we investigate in this paper how relaxing this simplification may affect the possibility of control. To investigate this phenomenon, we study two cases: that of a laser coupled only to a reaction coordinate which is in turn coupled to a “bath” mode, as compared to the case in which the laser is coupled both to the reaction coordinate and the environmental mode. In another closely related investigation, we study the effect of uncertainty introduced into the controlling pulse. The exact potential of a chemical reaction in solution cannot be known to perfect accuracy. Our results give insights into the challenges which will face attempts at condensed phase chemical reaction control, and point strongly to the need for adaptive algorithms for laser control pulse generation.

Control of tunneling in a symmetric double well coupled to a bath via an external field is demonstrated. Optimal control theory is employed to design a laser field which couples to the reaction coordinate and drives a localized wave packet on the reactant side to the product side at a specified target time τ. Both a very quantumlike system (high barrier) and a low barrier double well are examined; excellent results are obtained for a range of reduced bath viscosities. Analysis of the control fields and corresponding localization dynamics shows that the frequency components of the control field are more or less in resonance with eigenstates of the double well and that the laser field enhances the natural dynamics of the individual wells. Future extension to more complicated models where the field couples to the bath is discussed.

A theoretical analysis of the recent femtosecond photoassociation spectroscopy (FPAS) experiment on mercury [U. Marvet and M. Dantus, Chem. Phys. Lett. 245, 393 (1995)] is presented. It is shown that when a thermal distribution of diatom collision pairs is excited from a free to a bound electronic state on a time scale shorter than molecular vibration, an ensemble of coherent wave packets is produced. The dynamics of these wave packets created by the photoassociation pulse can be observed by firing a second probe pulse at variable time delays, and the depletion of the first excited bound state by the probe pulse is detected via fluorescence of the remaining population. Simulations of the FPAS experiment, using both wave packet propagation techniques and perturbation theory, clearly show the vibrational dynamics of the photoassociated transients. It is also demonstrated how the FPAS technique may be used as a tool for controlling the energy, impact parameter, and orientation in bimolecular reactions.

The crystal structures of the title compounds are based on corner-linked BO4 and SO4 tetrahedra with varying coordination of the alkali cations.

New alkali borosulfates were obtained by precipitation from oleum, solid-state reactions, or thermal decomposition. The crystal structures were characterized with single-crystal data. They are all based on corner-linked BO4 and SO4 tetrahedra with varying coordination of the alkali cations. According to the ratio of BO4 and SO4 tetrahedra, different frameworks are observed, i.e., noncondensed complex anions (1:4), one-dimensional chains (1:3), or three-dimensional (3D) networks (1:2). This is in analogy to silicates, where the ratio Si/O relates to the dimensionality also. For Na5[B(SO4)4], which exists in two different polymorphs, there are noncondensed pentameric units. Na5[B(SO4)4]-I: space group Pca21, a = 10.730(2) Å, b = 13.891(3) Å, c = 18.197(4) Å. Na5[B(SO4)4]-II: space group P212121, a = 8.624(2) Å, b = 9.275(2) Å, c = 16.671(3) Å. A3[B(SO4)3] (A = K, Rb) are isotypic with Ba3[B(PO4)3] adopting space group Ibca [K3[B(SO4)3], a = 7.074(4) Å, b = 14.266(9) Å, c = 22.578(14) Å; Rb3[B(SO4)3], a = 7.2759(5) Å, b = 14.7936(11) Å, c = 22.637(2) Å] with vierer chains of BO4tetrahedra based on two bridging and two terminal SO4 tetrahedra. Li[B(SO4)2] [space group Pc, a = 7.6353(15) Å, b = 9.342(2) Å, c = 8.432(2) Å, and β = 92.55(2)°] comprises a 3D network that is closely related to β-tridymite. Li[B(S2O7)2] [space group P212121, a = 10.862(2) Å, b = 10.877(2) Å, c = 17.769(4) Å] represents the first example of a disulfate complex with noncondensed [B(S2O7)2](-) units. Vibrational spectra were recorded from all compounds, and the thermal behavior was also investigated.

A new feedback algorithm to design laser fields for state-selective excitation of molecular systems is proposed. The population amplitudes and relative phases of the eigenstates are used to generate a field which drives the population flow in the desired direction. Results are presented for both vibrational excitation of hydrogen fluoride and selective excitation of one of two degenerate electronic states in a model four level system.

Advantages of the Fourier grid Hamiltonian method and the Floquet theory have been combined to fabricate a Fourier grid Floquet (FGF) propagator for economical treatment of long time photodynamics in the presence of intense laser fields. Initial applications to photodissociation of LiH and multiphoton dynamics of H2+ show that considerable computational economy is obtained with the use of the FGF propagator. A scheme for further economy through the use of a reduced FGF propagator is discussed and applied to multiphoton dissociation of H2+.

A detailed overview of nitric oxide and nitric oxide synthases in the kidney is presented. Physiologically, constitutive and inducible nitric oxide synthases have been detected in basically all vascular segments of the kidney, including all large vessels and arterioles that are primarily involved in the regulation of renal hemodynamics. It was observed that nitric oxide increases renal blood flow, decreases renal vascular resistance, and exerts variable effects on glomerular filtration rate depending on the experimental conditions. In addition, macula densa generated nitric oxide appears to mediate tubuloglomerular feedback. Constitutive and inducible nitric oxide synthases have also been delineated in most renal tubular segments. The inner medullary collecting duct was shown to contain the highest amount of constitutive nitric oxide synthase as compared to other nephron segments. It appears that nitric oxide may directly enhance tubular reabsorption in the collecting duct and the proximal tubule. Pressur...

A new time-dependent wavepacket approach has been applied to illustrate a rigorous method of calculating the transition function for bound-to-continuum transitions in translational energy spectrometric experiments. The method is numerically exact and fully quantal, and is devoid of any classical or semi-classical approximations. The validity of the hitherto-applied reflection approximation is investigated in a comparative study. The method has been applied to two different translational energy spectrometry experiments: collision-induced dissociation of CO + and collisional excitation of H 2 .

Excitation of molecular hydrogen has been studied in 1.8-keV collisions with molecular projectile ions H[sub 2][sup +], N[sub 2][sup +], CO[sup +], O[sub 2][sup +], and CO[sub 2][sup +] by means of energy-loss spectrometry using a high-resolution ion translational-energy spectrometer. Excitation of the target H[sub 2] is observed only in the case of collisions with [ital H][sub 2][sup +]. Oscillator strengths for electronic transitions to various electronic states are determined by simulating the measured energy-loss spectra with calculations using calculated Franck-Condon overlap integrals. Excitation of the projectile ions is observed in the case of collisions with N[sub 2][sup +] and CO[sup +] projectiles. Neither projectile excitation nor target excitation is observed when experiments are carried out with O[sub 2][sup +] and CO[sub 2][sup +] projectiles. The results obtained in the present study are interpreted as a manifestation of wave-function-overlap effects involving the highest occupied molecular orbitals of the target and projectile ions.

Control of IBr photodissociation branching ratios is explored using optimal control theory to design the requisite pulses which produce ground or spin—orbit excited bromine atoms. To conform to experimental pulse shaping limitations, these pulses are confined to a limited bandwidth and further modified by inspection of the power spectra from which extraneous frequency components are removed. Branching ratios using the filtered fields are shown to still provides appreciable selectivity, but with the added benefit of more feasible pulse shapes.

Simulations of the quantum dynamics of the HF molecule immersed in a field of five overlapping, intense, linearly polarized, infrared laser pulses of subpicosecond duration are performed. The HF molecule, initially in its ground state, is modeled as a rotating oscillator interacting with a classical laser field via electric dipole interaction. Realistic potential and dipole functions are used. Optimal overlaps of the five laser pulses, as well as the optimal carrier frequencies of the laser pulses, are found which maximize the HF dissociation yield. A maximal yield of 45% in a single combined pulse is achieved using the best available potential and dipole moment functions. The optimal infrared multiphoton dissociation pathway for the HF molecule includes a series of the Δv=1 vibrational‐rotational transitions followed by a series of Δv≥2 vibrational‐rotational transitions. The latter is necessary as a consequence of the vanishing Δv=1 transition moment around v=12. In the Δv=1 regime, both P and R branch ...

An optimization procedure for producing selective excitation of molecules undergoing stochastic dephasing collisions is presented. The collisional effects are incorporated by propagating the Schrodinger equation with random perturbations. The optimization procedure utilizes gradients of the perturbation‐averaged physical objective with respect to the laser field parameters; we demonstrate on a model problem that very few averages over collisional events suffice to yield converged results. Therefore, this method is computationally efficient because large averaging of dynamical simulations is not necessary. These results show the viability of the optimal control procedure for application to controlling chemical reactions in solution.

An iterative optimization algorithm for designing laser fields to control molecular motion which utilizes laboratory input (test fields) and output (resulting product yields) information is proposed. Laboratory uncertainties such as laser field noise and limited precision in the product yield measurements are included in the simulations of the experiments. Two simulated examples of implementation of the algorithm are presented: selective electronic excitation in a model four‐state system and maximizing dissociation yield of the hydrogen fluoride molecule. Both examples demonstrate that, even with the inclusion of laboratory uncertainties, the experimental learning‐based algorithm is a potentially feasible method of controlling molecular motion and possibly manipulating chemical reactions.

The technically challenging field of single-molecule biophysics has established itself in the last decade by granting access to detailed information about the fate of individual biomolecules, unattainable in traditional biochemical assays. The appeal of single-molecule methods lies in the directness of the information obtained from individual biomolecules. Technological improvements in single-molecule methods have made it possible to combine optical tweezers, fluorescence microscopy, and microfluidic flow systems. Such a combination of techniques has opened new possibilities to study complex biochemical reactions on the single-molecule level. In this chapter, we provide general considerations for the development of a combined optical trapping, fluorescence microscopy, and microfluidics instrument, along with methods to solve technical issues that are critical for designing successful experiments. Finally, we present several experiments to illustrate the power of this combination of techniques.

Controlling curve‐crossing dynamics of a model diatomic system between two dissociative electronic states through radiative coupling with a third bound state is examined. Starting with an initial wave packet on one of the crossing surfaces, optimal control theory is used to design the radiative field to either enhance or eliminate (at our choice) selectivity of one product channel over another. A new optimization procedure is introduced which filters out dc and low frequency components from the optimal field, but still allows for resonant transitions to a third bound state. This procedure forces the fields to employ interesting physical mechanisms involving the bound state in order to control the electronic branching ratios rather than directly negating or enhancing the diabatic coupling term in the Hamiltonian. A new propagation scheme for a multisurface Hamiltonian using Pauli matrices is also presented.

Single-molecule manipulation studies have revealed that double-stranded DNA undergoes a structural transition when subjected to tension. At forces that depend on the attachment geometry of the DNA (65 pN or 110 pN), it elongates ≈1.7-fold and its elastic properties change dramatically. The nature of this overstretched DNA has been under debate. In one model, the DNA cooperatively unwinds, while base pairing remains intact. In a competing model, the hydrogen bonds between base pairs break and two single DNA strands are formed, comparable to thermal DNA melting. Here, we resolve the structural basis of DNA overstretching using a combination of fluorescence microscopy, optical tweezers, and microfluidics. In DNA molecules undergoing the transition, we visualize double- and single-stranded segments using specific fluorescent labels. Our data directly demonstrate that overstretching comprises a gradual conversion from double-stranded to single-stranded DNA, irrespective of the attachment geometry. We found that these conversions favorably initiate from nicks or free DNA ends. These discontinuities in the phosphodiester backbone serve as energetically favorable nucleation points for melting. When both DNA strands are intact and no nicks or free ends are present, the overstretching force increases from 65 to 110 pN and melting initiates throughout the molecule, comparable to thermal melting. These results provide unique insights in the thermodynamics of DNA and DNA-protein interactions.

Cyclic voltammetry was employed to determine the formal reduction potential and heterogeneous electrontransfer rate constant of cytochrome c immobilized on three different metal substrates chemically modified with 11- mercaptoundoecanoic acid. The metal substrates include smooth gold and silver electrodes as well as nanoscopically rough silver electrodes obtained via an oxidation-reduction cycle. Electrode roughening followed a protocol typically employed to prepare surface-enhanced Raman active surfaces such that the electrochemical results can be compared with those determined by surface-enhanced resonance Raman spectroscopy of cytochrome c. The roughness of the surfaces was estimated by means of atomic force microscopy. For all systems midpoint potentials were found to be -0.068 V (vs SCE), although for rough silver electrode the midpoint potential slightly shifted in time from -0.051 V to -0.068 V within 24 h. The heterogeneous electron-transfer rate constants differ for the various metal substrates and were found to be smaller by a factor of 2.5 for the rough and smooth Ag substrates compared to Au electrodes. These findings imply that it is primarily the kind of metal rather than its surface morphology that controls the thermodynamics and kinetics of interfacial redox processes of immobilized cytochrome c. The present paper reconciles the partly conflicting results obtained by electrochemical methods, usually done on Au, and surface-enhanced resonance Raman spectroscopic techniques which are usually performed on Ag electrodes. © 2009 American Chemical Society.

The possibility of controlling unimolecular–dissociation processes with multiple laser fields in the collisional regime is examined. Employing the Bloch equations to describe optical excitation and decay processes, optimal control theory is used to design amplitude modulated fields which produce the desired excited‐state products. The selectivity of the product distribution of a simple four‐state photodissociation system is shown to have a square‐root dependence on the relative value of the mean dephasing time T2 to the pulse length τ, i.e, (T2/τ)1/2. The equivalence between T2 decay and phase disruptions occurring in a random‐walk fashion is also examined. In the Appendix it is shown that the essential effect of the system temperature is to introduce a Boltzmann population factor on the product selectivity without affecting the nature of the optimal field.

Ion channels in the apical cell membrane of monolayers of rabbit renal collecting duct principal cells in primary culture were investigated with the patch-clamp technique. Besides three or more types of cation channels published previously, three types of anion channels were observed. Most frequent was an outwardly rectifying Cl– selective channel with the slope conductance of 30.4 ± 4.8 pS (n = 6) in symmetrical isotonic NaCl solutions at 0 mV holding potential. This channel was only observed in excised patches. Its open probability was independent of the calcium concentration at the cytoplasmic surface of the membrane patch. The channel had complex open/close kinetics and was blocked by 5-nitro-2-(3-phenylpropylamino) benzoic acid from the extracellular surface. Inhibition increased at more cytoplasm-positive membrane potentials. Secondly, a high conductance, poorly selective anion channel was observed. It had a linear current voltage (I/V) relation with a conductance of 267 ± 46 pS (n = 4) and exhibited at least four substates. The open probability of this channel decreased sharply with increasing membrane potentials of either polarity. Thirdly, and least frequently, a bursting Cl– selective channel was observed which displayed a peculiar I/V relation in isotonic NaCl solutions. Near 0 mV it had a slope conductance of ≈ 50 pS which increased to 113 ± 11 pS (n = 4) at potentials exceeding ± 50 mV. Since the peritubular cell membrane of principal cells is Cl– permeable, it is conceivable that one or more of these channels contribute to collecting duct Cl– absorption particularly in situations in which the luminal Cl– concentration and the transepithelial potential difference are high.

One-phonon ionization of donors in germanium via intervalley scattering by slow TA phonons at the X point of the Brillouin zone is demonstrated by the stress dependence of phonoconductivity. Superconducting aluminum junctions are used as tunable quasimonochromatic phonon sources up to these extreme frequencies. The ionization probability is found to be increased when donor levels associated with stress-shifted higher valleys of the conduction band cross the lowest valley(s).

The apical cell membrane of cultured monolayers of collecting duct principal cells was investigated with the patch-clamp technique to study single ion channels. A broad spectrum of channel events was observed which complicated the analysis. Although principal cells absorb mainly Na+ ions and although most patches must have contained an Na+ conductance as evidenced by asymmetric clamp currents in the presence of amiloride, single Na+ channel events could not be identified with certainty, possibly because single-channel conductance was too low (≤5pS). Instead, non-selective cation channels of 21.2 ± 4.0 pS were frequently observed. They were impermeable to choline and anions but did not discriminate between Na+ and K+. These channels, however, do not appear to participate in active Na+ absorption. Different types of K+ channels were observed: a high-conductance Ca2+-activated K+ channel and a bursting low-conductance K+ channel. Since the former channel has been denied a role in K+ secretion/ absorption in native collecting ducts, the latter might be involved. In addition three types of CΓ channels have been observed which will be described separately. At least one of those, a 30-pS outwardly rectifying Cl- channel appears to allow small amounts of Cl- ions to be absorbed across principal cells.

Our objective was to determine the role of the Rho-associated kinase (ROK) for the regulation of FBF (FBF) and to unmask a potential role of ROK for the regulation of endothelium-derived nitric oxide (NO). Moreover, the effect of fasudil on the constrictor response to endothelin-1 was recorded. Regarding background, phosphorylation of the myosin light chain (MLC) determines the calcium sensitivity of the contractile apparatus. MLC phosphorylation depends on the activity of the MLC kinase and the MLC phosphatase. The latter enzyme is inhibited through phosphorylation by ROK. ROK has been suggested to inhibit NO generation, possibly via the inhibition of the Akt pathway. In this study, the effect of intra-arterial infusion of the ROK inhibitor fasudil on FBF in 12 healthy volunteers was examined by venous occlusion plethysmography. To unmask the role of NO, fasudil was infused during NO clamp. As a result, fasudil markedly increased FBF in a dose-dependent manner from 2.34 ± 0.21 to 6.96 ± 0.93 ml/100 ml forearm volume at 80 μg/min ( P < 0.001). At 1,600 μg/min, fasudil reduced systolic, diastolic, and mean arterial pressure while increasing heart rate. Fasudil abolished the vasoconstrictor effect of endothelin-1. The vascular response to fasudil (80 μmol/min) was blunted during NO clamp (104 ± 18% vs. 244 ± 48% for NO clamp + fasudil vs. fasudil alone; data as ratio between infused and noninfused arm with baseline = 0%, P < 0.05). In conclusion, 1) basal peripheral and systemic vascular tone depends on ROK; 2) a significant portion of fasudil-induced vasodilation is mediated by NO, suggesting that vascular bioavailable NO is negatively regulated by ROK; and 3) the constrictor response to endothelin involves the activation of ROK.