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1.
Allergy ; 73(1): 64-76, 2018 Jan.
Article in English | MEDLINE | ID: mdl-28771830

ABSTRACT

Regulatory approaches for allergen immunotherapy (AIT) products and the availability of high-quality AIT products are inherently linked to each other. While allergen products are available in many countries across the globe, their regulation is very heterogeneous. First, we describe the regulatory systems applicable for AIT products in the European Union (EU) and in the United States (US). For Europe, a depiction of the different types of relevant procedures, as well as the committees involved, is provided and the fundamental role of national agencies of the EU member states in this complex and unique network is highlighted. Furthermore, the regulatory agencies from Australia, Canada, Japan, Russia, and Switzerland provided information on the system implemented in their countries for the regulation of allergen products. While AIT products are commonly classified as biological medicinal products, they are made available by varying types of procedures, most commonly either by obtaining a marketing authorization or by being distributed as named patient products. Exemptions from marketing authorizations in exceptional cases, as well as import of allergen products from other countries, are additional tools applied by countries to ensure availability of needed AIT products. Several challenges for AIT products are apparent from this analysis and will require further consideration.


Subject(s)
Allergens/immunology , Desensitization, Immunologic , Hypersensitivity/immunology , Hypersensitivity/therapy , Allergens/administration & dosage , Desensitization, Immunologic/methods , Europe , Health Policy , Humans , Hypersensitivity/epidemiology , Practice Guidelines as Topic , United States
2.
Metallomics ; 6(7): 1181-97, 2014 Jul.
Article in English | MEDLINE | ID: mdl-24696003

ABSTRACT

Metallo-ß-lactamases are important as a major source of resistance of pathogenic bacteria to the widely used ß-lactam antibiotics. They show considerable diversity in terms of sequence and are grouped into three subclasses, B1, B2 and B3, which share a common overall fold. In each case the active enzyme has binding sites for two zinc ions in close proximity, although the amino-acid residues which coordinate the metals vary from one subclass to another. In subclasses B1 and B3, there has been controversy about whether both zinc ions are required for activity, but the most recent evidence indicates that there is positive cooperativity in zinc binding and that the catalytically relevant species is the di-zinc enzyme. Subclass B2 enzymes, on the other hand, are active in the mono-zinc state and are inhibited by the binding of a second zinc ion. Evidence for the importance of the zinc ions in substrate binding has come from structures of product complexes which indicate that the ß-lactam core binds to subclass B1 and B3 enzymes in a rather consistent fashion, interactions with the zinc ions being centrally important. The zinc ions play key roles in the catalytic mechanism, including facilitating nucleophilic attack on the amide carbonyl by the zinc-bound hydroxide ion, stabilising the anionic tetrahedral intermediate and coordinating the departing amine nitrogen.


Subject(s)
Zinc/metabolism , beta-Lactamases/chemistry , beta-Lactamases/metabolism , Binding Sites , Catalysis , Catalytic Domain , Models, Molecular , Substrate Specificity , beta-Lactams/metabolism
3.
Scand J Med Sci Sports ; 22(6): e156-67, 2012 Dec.
Article in English | MEDLINE | ID: mdl-22925166

ABSTRACT

The aim of this study was to examine the careers of two successful female elite athletes who later stagnated, and to identify possible factors that might have led to their demotivation. Individual interviews and a focus group interview were conducted. Using a multidisciplinary approach, the stories of April and Hazel raised several issues related to coaching, coach education, and the development of female athletes. Their individual profiles revealed that their perception of the lack of long-term development was caused by coach miscommunication, having to cope with sudden fame, and injuries provoked by overtraining. The coach-athlete relationship was discussed with a focus on the inexperience of some coaches, the number of coaches the athletes had to deal with, sociolinguistic issues, and the differing criteria of success communicated. Finally, the importance of their national governing bodies to focus on knowledge transfer, the supervision of coaches, and the infrastructure to monitor athletes were discussed.


Subject(s)
Athletes/psychology , Communication , Interpersonal Relations , Stress, Psychological/psychology , Adaptation, Psychological , Adult , Athletic Injuries/etiology , Exercise , Female , Health Knowledge, Attitudes, Practice , Humans , Interviews as Topic , Motivation , Norway , Organizational Policy , Sports/education , Sports/psychology , Sports/standards
4.
Scand J Med Sci Sports ; 22(4): 569-79, 2012 Aug.
Article in English | MEDLINE | ID: mdl-21210857

ABSTRACT

The purpose of this study was to investigate media and coach-athlete stress experienced by professional football players and their relationship to motivational variables by testing an achievement goal theory (AGT) stress model. In order to do so, we developed scales specifically designed to assess media and coach-athlete stress. Eighty-two elite football players (M(age) =25.17 years, SD=5.19) completed a series of questionnaires. Correlations and bootstrapping were used as primary statistical analyses, supplemented by LISREL, to test the hypotheses. Results revealed that a mastery climate was directly and negatively associated with coach-athlete stress, while a performance climate was directly and positively associated with coach-athlete stress. In addition, an indirect positive path between the performance climate and media stress was revealed through ego orientation. These findings support some of the key postulates of AGT; a mastery climate reduces the perception of stress among athletes, and the converse is true for a performance climate. Coaches of elite footballers are advised to try to reduce the emphasis on performance criteria because of its stress-reducing effects.


Subject(s)
Achievement , Athletes/psychology , Football , Goals , Interpersonal Relations , Mass Media , Stress, Psychological/psychology , Workplace , Adult , Humans , Male , Organizational Culture , Surveys and Questionnaires , Workplace/psychology , Young Adult
5.
Scand J Med Sci Sports ; 20(4): 686-95, 2010 Aug.
Article in English | MEDLINE | ID: mdl-19793212

ABSTRACT

Elite adolescent sport is a relatively unexplored research field. The purpose of this investigation was to examine how the Norwegian Olympic Youth Team (N=29) experienced competitive and organizational stress during the European Youth Olympic Festival in July 2007 and how they coped with the stressors. Participants were aged 14-17 and competed in handball, track and field, swimming, and judo. We used a qualitative methodology with interviews and open-ended questionnaires. Qualitative content analyses revealed that the athletes experienced competitive stressors because of the size and importance of the competition, and organizational stressors (e.g., housing, lining up for food, and transportation) exacerbated by the extreme heat during the Festival. The elite competitive experience was novel to all and overwhelming for some of the more "inexperienced" athletes. The athletes used cognitive coping strategies to some extent in addition to relying on different types of social support. The findings revealed the need for social support for adolescent athletes, and underlined the importance of a good coach-athlete relationship in order to perform well and enjoy the competitive experience.


Subject(s)
Adaptation, Psychological , Athletes/psychology , Competitive Behavior , Social Support , Sports , Adolescent , Anniversaries and Special Events , Female , Humans , Interviews as Topic , Male , Norway , Surveys and Questionnaires
6.
Scand J Med Sci Sports ; 19(1): 129-41, 2009 Feb.
Article in English | MEDLINE | ID: mdl-18248549

ABSTRACT

The purpose of this study was to investigate the effectiveness of an ongoing AIDS education intervention program (EMIMA) using peers in a sport context. A secondary purpose was to determine whether a mastery-based motivational strategy would enhance the effectiveness of the peer coaches. A quasi field experimental study was employed in which at-risk children in Dar es Salaam in Tanzania (N=764) were recruited (average age=13.6 years) and were randomly grouped into two treatment groups and two control groups. The treatment groups were peer coaches conducting the AIDS education to the children within sport, one with mastery coaching strategies and one without. The two control groups were in-school children, who received traditional AIDS education, and out-of-school children, who received no education at all. The intervention lasted for 8 weeks. The results indicated that the intervention using peers in sport was more effective in transmitting HIV prevention knowledge, cognitions and perceived behaviors than the control groups. The mastery-based motivational strategies were effective in influencing some of the variables. Contrary to expectation, the school-based HIV education was no more effective than the informal education obtained by the out-of-school children. The use of peer coaches within the EMIMA program was reliably the most effective means for HIV/AIDS education for these at-risk children.


Subject(s)
Football , HIV Infections/prevention & control , Health Education , Peer Group , Adolescent , Child , Female , Health Knowledge, Attitudes, Practice , Humans , Male , Surveys and Questionnaires
7.
Proc Natl Acad Sci U S A ; 105(21): 7370-5, 2008 May 27.
Article in English | MEDLINE | ID: mdl-18499803

ABSTRACT

Aerosol impacts on climate change are still poorly understood, in part, because the few observations and methods for detecting their effects are not well established. For the first time, the enhancement in cloud albedo is directly measured on a cloud-by-cloud basis and linked to increasing aerosol concentrations by using multiple autonomous unmanned aerial vehicles to simultaneously observe the cloud microphysics, vertical aerosol distribution, and associated solar radiative fluxes. In the presence of long-range transport of dust and anthropogenic pollution, the trade cumuli have higher droplet concentrations and are on average brighter. Our observations suggest a higher sensitivity of radiative forcing by trade cumuli to increases in cloud droplet concentrations than previously reported owing to a constrained droplet radius such that increases in droplet concentrations also increase cloud liquid water content. This aerosol-cloud forcing efficiency is as much as -60 W m(-2) per 100% percent cloud fraction for a doubling of droplet concentrations and associated increase of liquid water content. Finally, we develop a strategy for detecting aerosol-cloud interactions based on a nondimensional scaling analysis that relates the contribution of single clouds to albedo measurements and illustrates the significance of characterizing cloud morphology in resolving radiometric measurements. This study demonstrates that aerosol-cloud-albedo interactions can be directly observed by simultaneous observations below, in, and above the clouds.


Subject(s)
Aerosols/chemistry , Aircraft , Climate
8.
Scand J Med Sci Sports ; 18(6): 810-21, 2008 Dec.
Article in English | MEDLINE | ID: mdl-18208425

ABSTRACT

The present study is founded on achievement goal theory (AGT) and examines the relationship between motivation, social support and performance anxiety with team handball players (n=143) from 10 elite teams. Based on these theories and previous findings, the study has three purposes. First, it was predicted that the female athletes (n=69) would report more performance worries and more social support use than males (n=74). The findings support the hypothesis for anxiety, but not for social support use. However, females report that they felt social support was more available than males. Second, we predicted and found a positive relationship between the interaction of ego orientation and perceptions of a performance climate on performance anxiety, but only for females. As predicted, perceived ability mediated this relationship. Finally, we predicted that perceptions of a performance climate were related to the view that social support was less available especially for the male athletes. Simple correlation supports this prediction, but the regression analyses did not reach significance. Thus, we could not test for mediation of social support between motivational variables and anxiety. The results illustrate that fostering a mastery climate helps elite athletes tackle competitive pressure.


Subject(s)
Anxiety , Athletic Performance/psychology , Motivation , Self Efficacy , Social Support , Adaptation, Psychological , Female , Humans , Male , Sports , Surveys and Questionnaires
9.
Scand J Med Sci Sports ; 18(2): 221-34, 2008 Apr.
Article in English | MEDLINE | ID: mdl-17617173

ABSTRACT

The purpose of this study was to investigate athlete burnout from a social-cognitive perspective by examining the relationship between social cognitive motivational variables at the start of a season and signs of burnout in elite athletes at the end of the season. Participants were 141 (F=60, M=81) elite winter sport athletes competing in Alpine skiing, Biathlon, Nordic Combined, Nordic skiing, and Speed skating. Participants completed a comprehensive motivation assessment package at the start of the season and a further burnout inventory at season's end. Results indicated that motivational dispositions, measures of the achievement climate, perceived ability and dimensions of perfectionism were associated with burnout in a conceptually consistent manner. Furthermore, the elite athletes could be grouped into two motivational profiles based on variables measured at the start of the season, one being adaptive and the other maladaptive. At season's end, the two different motivational profiles yielded distinctively different responses on an inventory assessing signs of burnout. The current findings strengthen the claim that burnout in elite athletes may not simply be "motivation gone awry" as Gould has suggested, but an inevitable consequence of exhibiting a maladaptive motivational profile.


Subject(s)
Burnout, Professional , Cognition , Sports/psychology , Adolescent , Adult , Female , Humans , Male , Motivation , Norway , Surveys and Questionnaires
10.
Scand J Med Sci Sports ; 18(4): 526-38, 2008 Aug.
Article in English | MEDLINE | ID: mdl-17555543

ABSTRACT

The present study explored the relationship between task involvement and coping with stress in elite competition. Participants were 82 elite wrestlers, both male (n=60) and female (n=22), from four different European countries, age 16-37. The data for the study were gathered over an 18-month period, and both qualitative in-depth interviews (n=6) and quantitative approaches were used. The quantitative study measured motivation from an achievement goal theory perspective: achievement goal orientation [Perception of Success Questionnaire], perceptions of the motivational climate [Perceived Motivational Climate in Sport Questionnaire] and coping strategies (Brief COPE). The qualitative part explored motivation and coping in depth. As expected, task involved wrestlers coped better in competitive situations due to their use of more adaptive coping strategies. The wrestlers' experiences seemingly make them prefer to stay task involved and use adaptive coping strategies (both problem-focused and emotion-focused strategies) in competition.


Subject(s)
Adaptation, Psychological , Stress, Psychological , Wrestling/psychology , Adolescent , Adult , Female , Humans , Male , Task Performance and Analysis
11.
Br J Pharmacol ; 153 Suppl 1: S82-9, 2008 Mar.
Article in English | MEDLINE | ID: mdl-18026129

ABSTRACT

The cytochromes P450 (CYPs) comprise a vast superfamily of enzymes found in virtually all life forms. In mammals, xenobiotic metabolizing CYPs provide crucial protection from the effects of exposure to a wide variety of chemicals, including environmental toxins and therapeutic drugs. Ideally, the information on the possible metabolism by CYPs required during drug development would be obtained from crystal structures of all the CYPs of interest. For some years only crystal structures of distantly related bacterial CYPs were available and homology modelling techniques were used to bridge the gap and produce structural models of human CYPs, and thereby obtain useful functional information. A significant step forward in the reliability of these models came seven years ago with the first crystal structure of a mammalian CYP, rabbit CYP2C5, followed by the structures of six human enzymes, CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2D6 and CYP3A4, and a second rabbit enzyme, CYP2B4. In this review we describe as a case study the evolution of a CYP2D6 model, leading to the validation of the model as an in silico tool for predicting binding and metabolism. This work has led directly to the successful design of CYP2D6 mutants with novel activity-including creating a testosterone hydroxylase, converting quinidine from inhibitor to substrate, creating a diclofenac hydroxylase and creating a dextromethorphan O-demethylase. Our modelling-derived hypothesis-driven integrated interdisciplinary studies have given key insight into the molecular determinants of CYP2D6 and other important drug metabolizing enzymes.


Subject(s)
Cytochrome P-450 CYP2D6/chemistry , Cytochrome P-450 CYP2D6/drug effects , Cytochrome P-450 Enzyme System/chemistry , Cytochrome P-450 Enzyme System/metabolism , Pharmaceutical Preparations/metabolism , Animals , Cytochrome P-450 Enzyme System/drug effects , Drug Interactions , Humans , Models, Molecular , Substrate Specificity
12.
Biochem Soc Trans ; 34(Pt 5): 971-4, 2006 Nov.
Article in English | MEDLINE | ID: mdl-17052239

ABSTRACT

The role of dynamics in the function of proteins, from enzymes to signalling proteins, is widely recognized. In many cases, the dynamic process is a relatively localized one, involving motion of a limited number of key residues, while in others large-scale domain movements may be involved. These motions all take place within the context of a folded protein; however, there is increasing evidence for the existence of some proteins where a transition between folded and unfolded structures is required for function.


Subject(s)
Protein Folding , Proteins/chemistry , Proteins/metabolism , Kinetics , Models, Molecular , Protein Binding , Protein Conformation , Protein Denaturation , Talin/chemistry , Talin/metabolism
13.
Scand J Med Sci Sports ; 16(5): 358-63, 2006 Oct.
Article in English | MEDLINE | ID: mdl-16978256

ABSTRACT

The purpose of the present research was to develop and validate a Norwegian version of the sport anxiety scale (SAS-N), a multidimensional sport performance trait anxiety inventory. The SAS consists of three unique dimensions measuring somatic anxiety, worry and concentration disruption, respectively. The translation-back translation method was used in development of the SAS-N, and athletes from different sports in Norway (N=282) participated in the study. The findings are similar to those of the English original, and lend support for the use of this instrument with Norwegian athlete subjects.


Subject(s)
Anxiety/psychology , Sports/psychology , Surveys and Questionnaires , Adolescent , Adult , Anxiety/physiopathology , Attention , Factor Analysis, Statistical , Female , Humans , Male , Middle Aged , Norway
14.
Eur J Anaesthesiol ; 22(5): 328-32, 2005 May.
Article in English | MEDLINE | ID: mdl-15918378

ABSTRACT

BACKGROUND AND OBJECTIVE: An evaluation of post-craniotomy analgesia within the University Hospital of Wales Neurosurgical Unit, Cardiff, found that many patients were experiencing moderate to severe pain post-craniotomy. It was therefore decided to undertake a nationwide survey of analgesic practices in order to establish best practice guidelines and benchmark with other units. METHOD: A postal questionnaire was sent to the senior nurse of every Neurosurgical Directorate within the UK inquiring about the current, standard analgesic practices for post-craniotomy patients in their unit. RESULTS: Completed replies were received from 23 of the 33 centres (70%). Intramuscular (i.m.) codeine phosphate was found to be the principal first-line analgesic used post-craniotomy. Only three centres used morphine as the first-line analgesic and only one centre used patient controlled analgesia routinely. The majority of centres (82%) used balanced analgesia. Pain assessments were only carried out in 57% of centres and no centre used a validated pain assessment tool specifically for dysphasic patients. CONCLUSIONS: Codeine phosphate continues to be the mainstay of post-craniotomy analgesia, however, it is proposed that patient controlled analgesia with morphine is an efficacious and safe alternative.


Subject(s)
Analgesia/methods , Analgesics/therapeutic use , Craniotomy , Pain, Postoperative/drug therapy , Postoperative Care/methods , Surgery Department, Hospital/statistics & numerical data , Analgesia/statistics & numerical data , Benchmarking , Health Care Surveys , Humans , Institutional Practice/statistics & numerical data , Neurosurgery , Pain Measurement/methods , Pain Measurement/statistics & numerical data , Postoperative Care/statistics & numerical data , Surveys and Questionnaires , United Kingdom
15.
Biochem Soc Trans ; 31(Pt 3): 497-501, 2003 Jun.
Article in English | MEDLINE | ID: mdl-12773143

ABSTRACT

Cytochrome P450 reductase (CPR) is a diflavin enzyme responsible for electron donation to mammalian cytochrome P450 enzymes in the endoplasmic reticulum. Dissection of the enzyme into functional domains and studies by site-directed mutagenesis have enabled detailed characterization of the mechanism of electron transfer using stopped-flow and equilibrium-perturbation methods, and redox potentiometry. These studies and the mechanism of electron transfer in CPR are reported herein.


Subject(s)
NADPH-Ferrihemoprotein Reductase/metabolism , Amino Acid Sequence , Electron Transport , Humans , Kinetics , Tryptophan
16.
Scand J Med Sci Sports ; 12(1): 54-9, 2002 Feb.
Article in English | MEDLINE | ID: mdl-11985767

ABSTRACT

Recent research investigating the effect of the motivational climate has found that even elite athletes benefit from a mastery climate. The purpose of the present study was to obtain a deeper understanding of the importance of the climate surrounding an athlete and the role of the coach for elite athletes by conducting in-depth interviews with a group of athletes (n=7). The athletes also completed the Perception of Success Questionnaire (POSQ) and Perception of Motivational Climate Questionnaire (PMCQ) to measure motivational indices. All the athletes were very high on task orientation and moderate to high on ego orientation. Most of the athletes perceived a high mastery climate and a low performance climate. The athletes emphasized the importance of the coach as the creator of the climate, as well as their preference for a supportive and caring climate. This speaks for an emphasis on a mastery climate for elite athletes.


Subject(s)
Leadership , Motivation , Organizational Culture , Sports/psychology , Adult , Competitive Behavior , Female , Humans , Interviews as Topic , Male , Norway , Personality , Physical Education and Training/methods , Skiing/psychology
17.
Sci Eng Ethics ; 7(4): 507-20, 2001 Jul.
Article in English | MEDLINE | ID: mdl-11697007

ABSTRACT

Development of and influence on ethical beliefs were surveyed at a major research university campus. Courses were ranked by faculty and students as most important. Mentors were ranked eighth in a list of nine factors. Of the 1,152 returned student questionnaires, 97 (8.4%) made the effort to write comments, and of the 610 faculty questionnaires returned, 64 (10%) wrote comments. These comments were rich in detail and description.


Subject(s)
Education, Graduate/standards , Ethics , Mentors , Chi-Square Distribution , Education, Graduate/methods , Humans , Surveys and Questionnaires
18.
Sci Eng Ethics ; 7(4): 525-37; discussion 538-40, 2001 Jul.
Article in English | MEDLINE | ID: mdl-11697009

ABSTRACT

In this article, we focus on the mentoring process, and we argue that the internal and external pressures extant at research universities may create a research culture that may be antithetical to appropriate mentoring. We developed a scale based on motivation theory to determine the perceived research culture in departments and research laboratories, and a mentoring scale to determine approaches to mentoring graduate students. Participants were 610 faculty members across 49 departments at a research oriented university. The findings were that a mastery-oriented research climate and an outcome-oriented research climate were manifested at the university. More importantly, each research climate had its own unique impact on how the faculty approached mentoring graduate students. A mastery research climate was related to a more supportive approach to mentoring than the outcome research climate. We concluded by suggesting that the outcome research climate may have an adverse effect on effective mentoring and on maintaining research ethics.


Subject(s)
Education, Graduate/standards , Ethics , Mentors , Analysis of Variance , Culture , Factor Analysis, Statistical , Female , Humans , Male , Surveys and Questionnaires
19.
Biochemistry ; 40(45): 13439-47, 2001 Nov 13.
Article in English | MEDLINE | ID: mdl-11695890

ABSTRACT

NADPH-cytochrome P450 oxidoreductase (P450 reductase, EC 1.6.2.4) is an essential component of the P450 monooxygenase complex and binds FMN, FAD, and NADPH cofactors. Residues Tyr140 and Tyr178 are known to be involved in FMN binding. A third aromatic side chain, Phe181, is also located in the proximity of the FMN ring and is highly conserved in FMN-binding proteins, suggesting an important functional role. This role has been investigated by site-directed mutagenesis. Substitution of Phe181 with leucine or glutamine decreased the cytochrome c reductase activity of the enzyme by approximately 50%. Ferricyanide reductase activity was unaffected, indicating that the FAD domain was unperturbed. The mutant FMN domains were expressed in Escherichia coli, and the redox potentials and binding energies of their complexes with FMN were determined. The affinity for FMN was decreased approximately 50-fold in the Leu181 and Gln181 mutants. Comparison of the binding energies of the wild-type and mutant enzymes in the three redox states of FMN suggests that Phe181 stabilizes the FMN-apoprotein complex. The amide 1H and 15N resonances of the Phe181Leu FMN domain were assigned; comparison of their chemical shifts with those of the wild-type domain indicated that the effect of the substitution on FMN affinity results from perturbation of two loops which form part of the FMN binding site. The results indicate that Phe181 cooperates with Tyr140 and Tyr178 to play a major role in the binding and stability of FMN.


Subject(s)
Flavin Mononucleotide/metabolism , NADPH-Ferrihemoprotein Reductase/metabolism , Phenylalanine/metabolism , Amino Acid Substitution , Catalysis , Conserved Sequence , Cytochrome c Group/metabolism , Ferricyanides/metabolism , Humans , Magnetic Resonance Spectroscopy , Models, Molecular , Mutagenesis , Oxidation-Reduction , Phenylalanine/genetics
20.
J Am Chem Soc ; 123(42): 10329-35, 2001 Oct 24.
Article in English | MEDLINE | ID: mdl-11603983

ABSTRACT

The two metal sites in cadmium substituted beta-lactamase from Bacillus cereus 569/H/9 have been studied by NMR spectroscopy ((1)H, (15)N, and (113)Cd) and PAC spectroscopy ((111m)Cd). Distinct NMR signals from the backbone amides are identified for the apoenzyme and the mononuclear and binuclear cadmium enzymes. For the binuclear cadmium enzyme, two (113)Cd NMR signals (142 and 262 ppm) and two (111m)Cd PAC nuclear quadrupole interactions are observed. Two nuclear quadrupole interactions are also observed, with approximately equal occupancy, in the PAC spectra at cadmium/enzyme ratios < 1; these are different from those derived for the binuclear cadmium enzyme, demonstrating interaction between the two metal ion binding sites. In contrast to the observation from PAC spectroscopy, only one (113)Cd NMR signal (176 ppm) is observed at cadmium/enzyme ratios < 1. The titration of the metal site imidazole (N)H proton signals as a function of cadmium ion-to-enzyme ratio shows that signals characteristic for the binuclear cadmium enzyme appear when the cadmium ion-to-enzyme ratio is between 1 and 2, whereas no signals are observed at stoichiometries less than 1. The simplest explanation consistent with all data is that, at cadmium/enzyme ratios < 1, the single Cd(II) is undergoing exchange between the two metal sites on the enzyme. This exchange must be fast on the (113)Cd NMR time scale and slow on the (111m)Cd PAC time scale and must thus occur in a time regime between 0.1 and 10 micros.


Subject(s)
Cadmium/chemistry , Fura-2/analogs & derivatives , beta-Lactamases/chemistry , Bacillus cereus/enzymology , Binding Sites , Binding, Competitive , Cadmium/metabolism , Chelating Agents/chemistry , Chelating Agents/metabolism , Fluorescent Dyes/chemistry , Fluorescent Dyes/metabolism , Fura-2/chemistry , Fura-2/metabolism , Kinetics , Metalloproteins/chemistry , Metalloproteins/metabolism , Nuclear Magnetic Resonance, Biomolecular , Spectrometry, Gamma , beta-Lactamases/metabolism
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