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ConspectusNearly a century after its first description, configurationally stable axial chirality remains a rare feature in marketed drugs. In the development of the KRAS

Researchers have suggested that overconsumption of food, alcohol, and drugs could be explained by chronically elevated approach tendencies to rewarding but unhealthy stimuli. Here, we use the example of food to show that dysregulated rather than chronically elevated approach tendencies are associated with negative health outcomes. To this end, we developed a new smartphone-based paradigm to measure dynamic changes in food approach tendencies outside the laboratory (piloted with N = 48). We demonstrated in three pre-registered experiments (total N = 367) that food approach tendencies decrease from before to after people have eaten. We further show that in overweight and obese participants, these dynamics are disrupted, as their food approach tendencies increase rather than decrease after meals. In addition to showing these effects based on traditional reaction time-based food approach tendencies, we also demonstrate these patterns in a novel measure of response force—a measure that has long been used to study motivation in animals but has received little attention in humans. Together, our findings suggest that both reaction-time based, and force-based approach tendencies change dynamically in accordance with people’s need states and that disruptions in these dynamics are associated with negative health outcomes, such as overweight and obesity.

Most EGFR exon 20 insertion (EGFRex20ins) driver mutations in non–small cell lung cancer (NSCLC) are insensitive to approved EGFR tyrosine kinase inhibitors (TKI). To address the limitations of existing therapies targeting EGFR-mutated NSCLC, mobocertinib (TAK-788), a novel irreversible EGFR TKI, was specifically designed to potently inhibit oncogenic variants containing activating EGFRex20ins mutations with selectivity over wild-type EGFR. The in vitro and in vivo activity of mobocertinib was evaluated in engineered and patient-derived models harboring diverse EGFRex20ins mutations. Mobocertinib inhibited viability of various EGFRex20ins-driven cell lines more potently than approved EGFR TKIs and demonstrated in vivo antitumor efficacy in patient-derived xenografts and murine orthotopic models. These findings support the ongoing clinical development of mobocertinib for the treatment of EGFRex20ins-mutated NSCLC.Significance:No oral EGFR-targeted therapies are approved for EGFR exon 20 insertion (EGFRex20ins) mutation-driven NSCLC. Mobocertinib is a novel small-molecule EGFR inhibitor specifically designed to target EGFRex20ins mutants. Preclinical data reported here support the clinical development of mobocertinib in patients with NSCLC with EGFR exon 20 insertion mutations.See related commentary by Pacheco, p. 1617.This article is highlighted in the In This Issue feature, p. 1601

Supplementary Tables (S1-6) and Figures (S1-6)

Introduction: Over the last decades, our understanding of the cognitive, motivational, and neural processes involved in addictive behavior has increased enormously. A plethora of laboratory-based and cross-sectional studies has linked cognitive-behavioral measures to between-subject differences in drinking behavior. However, such laboratory-based studies inevitably suffer from small sample sizes and the inability to link temporal fluctuations in task measures to fluctuations in real-life substance use. To overcome these problems, several existing behavioral tasks have been transferred to smartphones to allow studying cognition in the field. Method: In this narrative review, we first summarize studies that used existing behavioral tasks in the laboratory and self-reports of substance use with ecological momentary assessment (EMA) in the field. Next, we review studies on psychometric properties of smartphone-based behavioral tasks. Finally, we review studies that used both smartphone-based tasks and self-reports with EMA in the field. Results: Overall, studies were scarce and heterogenous both in tasks and in study outcomes. Nevertheless, existing findings are promising and point toward several methodological recommendations: concerning psychometrics, studies show that – although more systematic studies are necessary – task validity and reliability can be improved, for example, by analyzing several measurement sessions at once rather than analyzing sessions separately. Studies that use tasks in the field, moreover, show that power can be improved by choosing sampling schemes that combine time-based with event-based sampling, rather than relying on time-based sampling alone. Increasing sampling frequency can further increase power. However, as this also increases the burden to participants, more research is necessary to determine the ideal sampling frequency for each task. Conclusion: Although more research is necessary to systematically study both the psychometrics of smartphone-based tasks and the frequency at which task measures fluctuate, existing studies are promising and reveal important methodological recommendations useful for researchers interested in implementing behavioral tasks in EMA studies.

Introduction: The emergence of Pavlovian-to-instrumental transfer (PIT) research in the human neurobehavioral domain has been met with increased interest over the past two decades. A variety of PIT tasks were developed during this time; while successful in demonstrating transfer phenomena, existing tasks have limitations that should be addressed. Herein, we introduce two PIT paradigms designed to assess outcome-specific and general PIT within the context of addiction. Materials and Methods: The single-lever PIT task, based on an established paradigm, replaced button presses with joystick motion to better assess avoidance behavior. The full transfer task uses alcohol and nonalcohol rewards associated with Pavlovian cues and instrumental responses, along with other gustatory and monetary rewards. We constructed mixed-effects models with the addition of other statistical analyses as needed to interpret various behavioral measures. Results: Single-lever PIT: both versions were successful in eliciting a PIT effect (joystick: p < 0.001, ηp2 = 0.36, button-box: p < 0.001, ηp2 = 0.30). Full transfer task: it was determined that the alcohol and nonalcoholic reward cues selectively primed their respective reward-associated responses (gustatory version: p < 0.001, r = 0.59, and monetary version: p < 0.001, r = 0.84). The appetitive/aversive cues resulted in a general transfer effect (gustatory: p < 0.001, ηp2 = 0.09, and monetary: p < 0.001, ηp2 = 0.17). Discussion/Conclusion: Single-lever PIT: PIT was observed in both task versions. We posit that the use of a joystick is more advantageous for the analysis of avoidance behavior. It evenly distributes movement between approach and avoid trials, which is relevant to analyzing fMRI data. Full transfer task: While gustatory conditioning has been used in the past to elicit transfer effects, we present the first paradigm that successfully elicits both specific and general transfers in humans with gustatory alcohol rewards.

Self-regulation, the ability to guide behavior according to one’s goals, plays an integral role in understanding loss of control behaviors a pertinent example being substance use disorders (SUD). Yet, experimental tasks that measure processes underlying self-regulation are not easy to deploy in contexts where such behaviors often occur, namely in real life situations outside the laboratory. Moreover, lab-based experimental tasks are criticized for poor test–retest reliability and a lack of construct validity. These concerns might in part explain why ecological validity of experimental measures—their ability to predict real-life behavior—is low. To address these shortcomings, we assessed the reliability and construct validity of four smartphone-based experimental tasks designed to measure cognitive control and decision-making. To facilitate future clinical applicability we recruited a large (N=488) sample of individuals with SUD. Joint modeling of measurement sessions increased the reliability of task measures from moderate to good and often excellent levels. In line with theories of cognitive control and motivation, three latent factors reflecting cognitive control and decision-making in the context of gains and losses best described the data. As proof of concept, we show that a latent cognitive control score based on joint modeling, yielded stronger correlations with drinking behavior than single task scores based on separate modeling. These findings indicate that in individuals with SUD, smartphone-based ambulatory experimental assessments can reliably index functions of cognitive control and decision-making, with plausible construct validity. Our findings provide evidence for rich possibilities arising from longitudinal experimental studies in SUD as well as in psychiatry, neuroscience, and psychology more generally.

Approach and avoidance tendencies have helped explain phenomena as diverse as addiction (Mogg, Field, & Bradley, 2005), phobia (Rinck & Becker, 2007), and intergroup discrimination (Bianchi, Carnaghi, & Shamloo, 2018; Degner, Essien, & Reichardt, 2016). When the original approach-avoidance task (AAT; Solarz, 1960) that measures these tendencies was redesigned to run on regular desktop computers, it made the task much more flexible but also sacrificed some important behavioral properties of the original task—most notably its reliance on physical distance change (Chen & Bargh, 1999). Here, we present a new, mobile version of the AAT that runs entirely on smartphones and combines the flexibility of modern tasks with the behavioral properties of the original AAT. In addition, it can easily be deployed in the field and, next to traditional reaction time measurements, includes the novel measurement of response force. In two studies, we demonstrate that the mobile AAT can reliably measure known approach-avoidance tendencies toward happy and angry faces both in the laboratory and in the field.

Aims/hypothesis. Pharmacological conditioning, where an association is formed between a drug and a conditioned stimulus (CS, e.g., smell), can influence physiological processes. Evidence exists that it is possible to condition insulin effects in animals and healthy humans but it is unclear whether these effects can be observed in patients as well. The aim of this study was to investigate the effects of pharmacological conditioning with intranasal insulin on blood glucose, insulin, c-peptide, hunger and memory in patients with diabetes type-2 and age- and sex-matched healthy controls. Exploratively, we examined sex differences in these effects. We hypothesized that conditioning with insulin would trigger endogenous insulin release, decrease blood glucose and hunger, and improve memory. Methods. In a randomized double-blind controlled trial, thirty-two patients with diabetes type-2 (17 males, mean age=68.8, SD=11.86) and thirty-two healthy controls (17 males, mean age=67.8, SD=6.12) were randomly assigned to a conditioned or a control group. On day 1, participants in the conditioned group received 6 administrations of 20 units of intranasal insulin together with a CS (smell of rosewood oil) while the control group received a placebo with the CS. On day 2, participants in both groups received a placebo spray with the CS. Glucose, insulin and c-peptide were repeatedly measured in blood on both days. Hunger was measured with a self-report question, a mobile approach-avoidance task and a taste test. Memory was measured with an auditory verbal learning test.Results. Intranasal insulin prevented the drop of glucose levels in patients but not in healthy controls (B=0.03, SE=0.02, p=0.027), and decreased C-peptide levels in healthy controls but not patients (B=0.01, SE=0.001, p=0.008). Conditioned insulin effects also prevented the drop of blood glucose levels but only in male participants (for both healthy and patient groups) (B=0.001, SE=0.0003, p=0.024). Moreover, conditioning significantly decreased hunger in healthy participants (B=0.31, SE=0.09, p< 0.001). No effects of intranasal insulin or conditioning were found on insulin, approach-avoidance tendencies, calories eaten and memory. Conclusions/interpretation. Our study provides further evidence that conditioning with intranasal insulin might modify blood glucose levels and decrease hunger and that its effects differ depending on health status and sex. The unexpected direction of intranasal insulin effects on blood glucose might potentially be explained by age as our study population was older than participants from previous research. Conditioning with intranasal insulin might be beneficial for groups suffering from intensive hunger, but seems not be particularly suitable for blood glucose reduction. Diabetes type-2 patients might benefit from conditioning with glucose lowering drugs.

In the treatment of non-small cell lung cancer (NSCLC), patients harboring exon 20 insertion mutations in the epidermal growth factor receptor (EGFR) gene (EGFR) have few effective therapies because this subset of mutants is generally resistant to most currently approved EGFR inhibitors. This report describes the structure-guided design of a novel series of potent, irreversible inhibitors of EGFR exon 20 insertion mutations, including the V769_D770insASV and D770_N771insSVD mutants. Extensive structure-activity relationship (SAR) studies led to the discovery of mobocertinib (compound 21c), which inhibited growth of Ba/F3 cells expressing the ASV insertion with a half-maximal inhibitory concentration of 11 nM and with selectivity over wild-type EGFR. Daily oral administration of mobocertinib induced tumor regression in a Ba/F3 ASV xenograft mouse model at well-tolerated doses. Mobocertinib was approved in September 2021 for the treatment of adult patients with advanced NSCLC with EGFR exon 20 insertion mutations with progression on or after platinum-based chemotherapy.

Introduction: Positively conditioned Pavlovian cues tend to promote approach and negative cues promote withdrawal in a Pavlovian-to-instrumental transfer (PIT) paradigm, and the strength of this PIT effect was associated with the subsequent relapse risk in alcohol-dependent (AD) patients. When investigating the effect of alcohol-related background cues, instrumental approach behavior was inhibited in subsequent abstainers but not relapsers. An automatic approach bias towards alcohol can be modified using a cognitive bias modification (CBM) intervention, which has previously been shown to reduce the relapse risk in AD patients. Here we examined the effects of such CBM training on PIT effects and explored its effect on the relapse risk in detoxified AD patients. Methods: N = 81 recently detoxified AD patients performed non-drug-related and drug-related PIT tasks before and after CBM versus placebo training. In addition, an alcohol approach/avoidance task (aAAT) was performed before and after the training to assess the alcohol approach bias. Patients were followed up for 6 months. Results: A stronger alcohol approach bias as well as a stronger non-drug-related PIT effect predicted relapse status in AD patients. No significant difference regarding relapse status or the number of heavy drinking days was found when comparing the CBM training group versus the placebo group. Moreover, there was no significant modulation effect of CBM training on any PIT effect or the aAAT. Conclusion: A higher alcohol approach bias in the aAAT and a stronger non-drug-related PIT effect both predicted relapse in AD patients, while treatment outcome was not associated with the drug-related PIT effect. Unlike expected, CBM training did not significantly interact with the non-drug-related or the drug-related PIT effects or the alcohol approach bias.

Implicit (‘unconscious’) approach–avoidance tendencies towards stimuli can be measured using the Approach Avoidance Task (AAT). We recently expanded a toolbox for analyzing the raw data of a novel, mobile version of the AAT (mAAT), that asks participants to move their phone towards their face (pull) or away (push) in response to images presented on the phone. We here tested the mAAT reaction time and the mAAT distance in a study with 71 Dutch participants that were recruited online and performed an experiment without coming to the laboratory. The participants used both the mAAT and (explicit) rating scales to respond to photographic images of food. As hypothesized, the rated wanting, rated valence and mAAT reaction time indicated a preference for palatable over unpalatable food, and for Dutch over Asian food. Additionally, as expected, arousal was rated higher for unpalatable than for palatable food, and higher for Dutch than for Asian food. The mAAT distance indicated that the unpalatable food images were moved across larger distances, regardless of the movement direction (pull or push), compared to the palatable food images; and the Dutch food images were moved across larger distances than the Asian food images. We conclude that the mAAT can be used to implicitly probe approach–avoidance motivation for complex images in the food domain. The new measure of mAAT distance may be used as an implicit measure of arousal. The ratings and the mAAT measures do not reflect the exact same information and may complement each other. Implicit measures, such as mAAT variables, are particularly valuable when response biases that can occur when using explicit ratings are expected.

Most

The statistics of the sum of random weights where the number of weights is Poisson distributed has important applications in nuclear physics, particle physics and astrophysics. Events are frequently weighted according to their acceptance or relevance to a certain type of reaction. The sum is described by the compound Poisson distribution (CPD) which is shortly reviewed. It is shown that the CPD can be approximated by a scaled Poisson distribution (SPD). The SPD is applied to parameter estimation in situations where the data are distorted by resolution effects. It performs considerably better than the normal approximation that is usually used. A special Poisson bootstrap technique is presented which permits to derive confidence limits for observations following the CPD., Comment: 14 pages, 2 figures

The gluon momentum density xg ( x , Q 2 ) of the proton was extracted at Q 2 = 20 GeV 2 for small values of x between 4 × 10 −4 and 10 −2 from the scaling violations of the proton structure function F 2 measured recently by ZEUS in deep inelastic neutral current ep scattering at HERA. The extraction was performed in two ways. Firstly, using a global NLO fit to the ZEUS data on F 2 at low x constrained by measurementsfrom NMC at larger x ; and secondly using published approximate methods for the solution of the GLAP QCD evolution equations. Consistent results are obtained. A substantial increase of the gluon density is found at small x in comparison with the NMC result obtained at larger values of x .

The decay mode K L → π 0 γγ has been observed with a signal of 21 events and an expected background of 1.5±0.9 events. A branching ratio for decays with invariant γγ masses above 280 MeV of (2.1±0.6)×10 −6 is calculated. This result is compared with the values estimated from theoretical models and has implications for the CP conserving contribution to K L → π 0 e + e − decay.

W-band (95 GHz) electron spin echo envelope modulation (ESEEM) is proposed as a method for simultaneously determining the relative orientation and separation of the constituents of spin-correlated radical pairs in the solid state. The discussion focuses on the transient secondary radical pair in bacterial photosynthetic energy conversion. © 2001 Elsevier Science B.V.

The decay rates of K L → 2γ and K S → 2γ have been measured at the CERN SPS. The results are Γ (K L →2 γ )/ χ (K L →2 π 0 )=0.632±0.004±0.008 and Γ (K S →2 γ )/ Γ (K L →2 γ )=2.3 ±1.0±0.4. This is the first observation of K S →2γ decays.

Common wisdom has it that Buddhism enhances compassion and self-other integration. We put this assumption to empirical test by comparing practicing Taiwanese Buddhists with well-matched atheists. Buddhists showed more evidence of self-other integration in the social Simon task, which assesses the degree to which people co-represent the actions of a coactor. This suggests that self-other integration and task co-representation vary as a function of religious practice.

Thrombus (blood clot) is implicated in a number of life threatening diseases, e.g., heart attack, stroke, pulmonary embolism. EP-2104R is an MRI contrast agent designed to detect thrombus by binding to the protein fibrin, present in all thrombi. EP-2104R comprises an 11 amino acid peptide derivatized with 2 GdDOTA-like moieties at both the C- and N-terminus of the peptide (4 Gd in total). EP-2104R was synthesized by a mixture of solid phase and solution techniques. The La(III) analogue was characterized by and 1D and 2D NMR spectroscopy and was found to have the expected structure. EP-2104R was found to be significantly more inert to Gd(III) loss than commercial contrast agents. At the most extreme conditions tested (pH 3, 60 degrees C, 96 hrs), less than 10% of Gd was removed from EP-2104R by a challenge with a DTPA based ligand, while the commercial contrast agents equilibrated within minutes to hours. EP-2104R binds equally to two sites on human fibrin (Kd = 1.7 +/- 0.5 microM) and has a similar affinity to mouse, rat, rabbit, pig, and dog fibrin. EP-2104R has excellent specificity for fibrin over fibrinogen (over 100-fold) and for fibrin over serum albumin (over 1000-fold). The relaxivity of EP-2104R bound to fibrin at 37 degrees C and 1.4 T was 71.4 mM(-1) s(-1) per molecule of EP-2104R (17.4 per Gd), about 25 times higher than that of GdDOTA measured under the same conditions. Strong fibrin binding, fibrin selectivity, and high molecular relaxivity enable EP-2104R to detect blood clots in vivo.

Choline kinase α (ChoKα) is an enzyme involved in the synthesis of phospholipids and thereby plays key roles in regulation of cell proliferation, oncogenic transformation, and human carcinogenesis. Since several inhibitors of ChoKα display antiproliferative activity in both cellular and animal models, this novel oncogene has recently gained interest as a promising small molecule target for cancer therapy. Here we summarize our efforts to further validate ChoKα as an oncogenic target and explore the activity of novel small molecule inhibitors of ChoKα. Starting from weakly binding fragments, we describe a structure based lead discovery approach, which resulted in novel highly potent inhibitors of ChoKα. In cancer cell lines, our lead compounds exhibit a dose-dependent decrease of phosphocholine, inhibition of cell growth, and induction of apoptosis at low micromolar concentrations. The druglike lead series presented here is optimizable for improvements in cellular potency, drug target residence time, and pharmacokinetic parameters. These inhibitors may be utilized not only to further validate ChoKα as antioncogenic target but also as novel chemical matter that may lead to antitumor agents that specifically interfere with cancer cell metabolism.

A novel methodology based on electron-nuclear double resonance (ENDOR) spectroscopy is used for the direct determination of the water coordination number (q) of gadolinium-based magnetic resonance imaging (MRI) contrast agents. Proton ENDOR spectra can be obtained at approximately physiological concentrations for metal complexes in frozen aqueous solutions either in the presence or absence of protein targets. It is shown that, depending on the structure of the co-ligand, the water hydration number of a complex in aqueous solution can be significantly different to when the complex is noncovalently bound to a protein. From the ENDOR spectra of the exchangeable protons, precise information on the metal-proton distance can be derived as well. These essential parameters directly correlate with the efficacy of MRI contrast agents and should therefore aid the development of novel, highly efficient compounds targeted to various proteins.

The synthesis of a novel ligand, based on N-methyl-diethylenetriaminetetraacetate and containing a diphenylcyclohexyl serum albumin binding group (L1) is described and the coordination chemistry and biophysical properties of its Gd(III) complex Gd-L1 are reported. The Gd(III) complex of the diethylenetriaminepentaacetate analogue of the ligand described here (L2) is the MRI contrast agent MS-325. The effect of converting an acetate to a methyl group on metal-ligand stability, hydration number, water-exchange rate, relaxivity, and binding to the protein human serum albumin (HSA) is explored. The complex Gd-L1 has two coordinated water molecules in solution, that is, [Gd(L1)(H2O)2]2- as shown by D-band proton ENDOR spectroscopy and implied by 1H and 17O NMR relaxation rate measurements. The Gd-H(water) distance of the coordinated waters was found to be identical to that found for Gd-L2, 3.08 A. Loss of the acetate group destabilizes the Gd(III) complex by 1.7 log units (log K(ML) = 20.34) relative to the complex with L2. The affinity of Gd-L1 for HSA is essentially the same as that of Gd-L2. The water-exchange rate of the two coordinated waters on Gd-L1 (k(ex) = 4.4x10(5) s(-1)) is slowed by an order of magnitude relative to Gd-L2. As a result of this slow water-exchange rate, the observed proton relaxivity of Gd-L1 is much lower in a solution of HSA under physiological conditions (r1(obs) = 22.0 mM(-1) s(-1) for 0.1 mM Gd-L1 in 0.67 mM HSA, HEPES buffer, pH 7.4, 35 degrees C at 20 MHz) than that of Gd-L2 (r1(obs) = 41.5 mM(-1) s(-1)) measured under the same conditions. Despite having two exchangeable water molecules, slow water exchange limits the potential efficacy of Gd-L1 as an MRI contrast agent.

A monolithically integrated micro flow sensor (MFS) for lab-on-chip application is presented. The MFS utilizes a miniaturized adaption of the anemometric principle. The combination of an established detection principle with the benefits of microtechnology results in a sensor with very high sensitivity. The temperature distribution in the microfluidic channel is simulated and compared with experimental results. The experimental investigation confirms that the micro MFS is able to detect flow rates as low as 10nl/min.

We introduce a new statistical quantity, the energy, to test whether two samples originate from the same distributions. The energy is a simple logarithmic function of the distances of the observations in the variate space. The distribution of the test statistic is determined by a resampling method. The power of the energy test in one dimension was studied for a variety of different test samples and compared to several nonparametric tests. In two and four dimensions, a comparison was performed with the Friedman–Rafsky and nearest neighbor tests. The two-sample energy test was shown to be especially powerful in multidimensional applications.

We introduce the novel concept of statistical energy as a statistical tool. We define statistical energy of statistical distributions in a similar way as for electric charge distributions. Charges of opposite sign are in a state of minimum energy if they are equally distributed. This property is used to check whether two samples belong to the same parent distribution, to define goodness-of-fit tests and to unfold distributions distorted by measurement. The approach is binning-free and especially powerful in multidimensional applications.

Inclusive differential cross sections dsigma(pA)/dx(F) and dsigma(pA)/dp(t)(2) for the production of K-S(0), Lambda, and (U) over bar particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to roots = 41.6 GeV in the proton-nucleon system. The ratios of differential cross sections dsigma(pA)(K-S(0))/dsigma(pA)(Lambda) and dsigma(pA)((U) over bar)/dsigma(pA) (Lambda) are measured to be 6.2 +/- 0.5 and 0.66 +/- 0.07, respectively, for x(F) approximate to -0.06. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions da,Ald t also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections sigma(pA) on the atomic mass A of the target material is discussed, and the deduced cross sections per nucleon sigma(pN) are compared with results obtained at other energies.

The Photosystem I (PS I) reaction center contains two branches of nearly symmetric cofactors bound to the PsaA and PsaB heterodimer. From the x-ray crystal structure it is known that Trp697PsaA and Trp677PsaB are π-stacked with the head group of the phylloquinones and are H-bonded to Ser692PsaA and Ser672PsaB, whereas Arg694PsaA and Arg674PsaB are involved in a H-bonded network of side groups that connects the binding environments of the phylloquinones and FX. The mutants W697FPsaA, W677FPsaB, S692CPsaA, S672CPsaB, R694APsaA, and R674APsaB were constructed and characterized. All mutants grew photoautotrophically, yet all showed diminished growth rates compared with the wild-type, especially at higher light intensities. EPR and electron nuclear double resonance (ENDOR) studies at both room temperature and in frozen solution showed that the PsaB mutants were virtually identical to the wild-type, whereas significant effects were observed in the PsaA mutants. Spin polarized transient EPR spectra of the P700+A1– radical pair show that none of the mutations causes a significant change in the orientation of the measured phylloquinone. Pulsed ENDOR spectra reveal that the W697FPsaA mutation leads to about a 5% increase in the hyperfine coupling of the methyl group on the phylloquinone ring, whereas the S692CPsaA mutation causes a similar decrease in this coupling. The changes in the methyl hyperfine coupling are also reflected in the transient EPR spectra of P700+A1– and the CW EPR spectra of photoaccumulated A1–. We conclude that: (i) the transient EPR spectra at room temperature are predominantly from radical pairs in the PsaA branch of cofactors; (ii) at low temperature the electron cycle involving P700 and A1 similarly occurs along the PsaA branch of cofactors; and (iii) mutation of amino acids in close contact with the PsaA side quinone leads to changes in the spin density distribution of the reduced quinone observed by EPR.

The directionality of electron transfer in Photosystem I (PS I) is investigated using site-directed mutations in the phylloquinone (QK) and FX binding regions of Synnechocystis sp. PCC 6803. The kinetics of forward electron transfer from the secondary acceptor A1 (phylloquinone) were measured in mutants using time-resolved optical difference spectroscopy and transient EPR spectroscopy. In whole cells and PS I complexes of the wild-type both techniques reveal a major, slow kinetic component of tau approximately 300 ns while optical data resolve an additional minor kinetic component of tau approximately 10 ns. Whole cells and PS I complexes from the W697FPsaA and S692CPsaA mutants show a significant slowing of the slow kinetic component, whereas the W677FPsaB and S672CPsaB mutants show a less significant slowing of the fast kinetic component. Transient EPR measurements at 260 K show that the slow phase is approximately 3 times slower than at room temperature. Simulations of the early time behavior of the spin polarization pattern of P700+A1-, in which the decay rate of the pattern is assumed to be negligibly small, reproduce the observed EPR spectra at 260 K during the first 100 ns following laser excitation. Thus any spin polarization from P700+FX- in this time window is very weak. From this it is concluded that the relative amplitude of the fast phase is negligible at 260 K or its rate is much less temperature-dependent than that of the slow component. Together, the results demonstrate that the slow kinetic phase results from electron transfer from QK-A to FX and that this accounts for at least 70% of the electrons. Although the assignment of the fast kinetic phase remains uncertain, it is not strongly temperature dependent and it represents a minor fraction of the electrons being transferred. All of the results point toward asymmetry in electron transfer, and indicate that forward transfer in cyanobacterial PS I is predominantly along the PsaA branch.

Using data collected by the HERA-B experiment, we have measured the fraction of J\psi's produced via radiative chi_c decays in interactions of 920 GeV protons with carbon and titanium targets. We obtained R_{\chi_c} = 0.32 \pm 0.06_{stat} \pm 0.04_{sys} for the fraction of J\psi from chi_c decays averaged over proton-carbon and proton-titanium collisions. This result is in agreement with previous measurements and is compared with theoretical predictions., Comment: 16 pages, 5 figs

Using the HERA-B detector, the b-bbar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b-bbar production was tagged via inclusive bottom quark decays into J/psi, by exploiting the longitudinal separation of J/psi->ll decay vertices from the primary proton-nucleus interaction. Both $e^+e^-$ and $\mu^+\mu^-$ channels have been reconstructed and the combined analysis yields the cross section $\sigma(b \bar b) = 32 ^{+14}_{-12} (stat) ^{+6}_{-7} (sys) nb/nucleon$., Comment: 22 pages, 10 Postscript figures

Pearson's χ 2 test for the comparison of histograms to a theoretical prediction is generalized to the case where the histogram contains weighted events.

1,4-Naphthoquinone (NQ) and its monosubstituted derivatives, 2-methyl, 2-ethyl, and 2-butyl-1,4-naphthoquinone, have been incorporated into the A1 binding site of photosystem I (PS I) after organic solvent extraction of the native phylloquinone. The charge separated state P700+NQ- has been studied by multifrequency transient EPR. The Q-band (35 GHz) spectra of fully deuterated 2-methyl-1,4-NQ-d8 and 2-ethyl-1,4-NQ-d10 show sufficient spectral resolution for the orientation of the quinone g tensor and thus the headgroup of the molecule to be determined. All orientation parameters of the substituted NQs are found to be the same as those established for native phylloquinone in PS I. However, for 2-ethyl-1,4-NQ and 2-butyl-1,4-NQ the X- and Q-band spectra exhibit a well resolved 1:2:1 hyperfine splitting. From the fact that it is absent when the first methylene group of the side chain is selectively deuterated, the splitting is assigned to the hyperfine coupling of the methylene protons. The principal values of the axially symmetric hyperfine coupling tensor are determined to be |Axx| = 12.2 MHz, |Ayy| = 16.8 MHz, |Azz| = 12.2 MHz, and aiso = 13.7 MHz. The large methylene proton hyperfine coupling arises from a high spin density on the ring carbon atom to which the alkyl tail is attached. This in turn suggests that only one of the carbonyl groups of 2-alkyl-1,4-NQ is H-bonded to the protein and that the alkyl tail must be in the ortho position relative to the carbonyl group with the H bond. This implies that the alkyl side chain of the substituted NQs resides in the space normally occupied by the methyl group of phylloquinone and not that of the phytyl tail, which is meta to the H-bonded carbonyl group according to the X-ray structure. In addition, the hyperfine tensor indicates that the first two C−C bonds of the alkyl tail must be coplanar with the aromatic ring. However, the X-ray structure of PS I shows, for the native phylloquinone, that the phytyl tail is bent out of the quinone plane with the second C−C bond.