Counterions determine uptake and effects of aluminum in human intestinal and liver cells.

Aluminum (Al) is highly abundant in the biosphere and can occur in different physico-chemical states. It is present in human food and undergoes transitions between dissolved and particulate species during the passage of the gastrointestinal tract. Moreover, in a complex matrix such as food different inorganic and organic counterions can affect the chemical behavior of Al following oral uptake. In this work, the effects of different counterions, namely chloride, citrate, sulfate, lactate and acetylacetonate, on Al uptake and toxicity in the human intestine are studied. The respective Al salts showed different dissolution behavior in biological media and formed nanoscaled particles correlating in reverse with the amount of their dissolved fraction. The passage through the intestinal barrier was studied using a Caco-2 Transwell® system, showing counterion-dependent variance in cellular uptake and transport. In addition, Al toxicity was investigated using Al species (Al3+, metallic Al0 and oxidic γAl2O3 nanoparticles) and counterions individually or in mixtures on Caco-2 and HepG2 cells. The strongest toxicity was observed using a combination of Al species, depending on solubility, and the lipophilic counterion acetylacetonate. Notably, only the combination of both led to toxicity, while both substances individually did not show toxic effects. A toxification of previously non-toxic Al-species by the presence of acetylacetonate is shown here for the first time. The dependency on the concentration of free Al ions was demonstrated using sodium hydrogen phosphate, which was able to counteract the toxic effects by complexing free Al ions. These findings, using Al salts as an example for a common food contaminant, underline the importance of a consideration of the chemical properties of human nutrition, especially dissolution and hydrophobicity, which can significantly influence the cellular uptake and effects of xenobiotic substances.

Spectroscopic glimpses of the transition state of ATP hydrolysis trapped in a bacterial DnaB helicase.

The ATP hydrolysis transition state of motor proteins is a weakly populated protein state that can be stabilized and investigated by replacing ATP with chemical mimics. We present atomic-level structural and dynamic insights on a state created by ADP aluminum fluoride binding to the bacterial DnaB helicase from Helicobacter pylori. We determined the positioning of the metal ion cofactor within the active site using electron paramagnetic resonance, and identified the protein protons coordinating to the phosphate groups of ADP and DNA using proton-detected 31P,1H solid-state nuclear magnetic resonance spectroscopy at fast magic-angle spinning > 100 kHz, as well as temperature-dependent proton chemical-shift values to prove their engagements in hydrogen bonds. 19F and 27Al MAS NMR spectra reveal a highly mobile, fast-rotating aluminum fluoride unit pointing to the capture of a late ATP hydrolysis transition state in which the phosphoryl unit is already detached from the arginine and lysine fingers.

Formulation and Characterization of Microcapsules Encapsulating PC12 Cells as a Prospective Treatment Approach for Parkinson's Disease.

Parkinson's disease (PD) is the second most common neurological disorder, associated with decreased dopamine levels in the brain. The goal of this study was to assess the potential of a regenerative medicine-based cell therapy approach to increase dopamine levels. In this study, we used rat adrenal pheochromocytoma (PC12) cells that can produce, store, and secrete dopamine. These cells were microencapsulated in the selectively permeable polymer membrane to protect them from immune responses. For fabrication of the microcapsules, we used a modified Buchi spray dryer B-190 that allows for fast manufacturing of microcapsules and is industrially scalable. Size optimization of the microcapsules was performed by systematically varying key parameters of the spraying device. The short- and long-term stabilities of the microcapsules were assessed. In the in vitro study, the cells were found viable for a period of 30 days. Selective permeability of the microcapsules was confirmed via dopamine release assay and micro BCA protein assay. We found that the microcapsules were permeable to the small molecules including dopamine and were impermeable to the large molecules like BSA. Thus, they can provide the protection to the encapsulated cells from the immune cells. Griess's assay confirmed the non-immunogenicity of the microcapsules. These results demonstrate the effective fabrication of microcapsules encapsulating cells using an industrially scalable device. The microcapsules were stable, and the cells were viable inside the microcapsules and were found to release dopamine. Thus, these microcapsules have the potential to serve as the alternative or complementary treatment approach for PD.

Binding of a Fatty Acid-Functionalized Anderson-Type Polyoxometalate to Human Serum Albumin.

The Anderson-type hexamolybdoaluminate functionalized with lauric acid (LA), (TBA)3[Al(OH)3Mo6O18{(OCH2)3CNHCOC11H23}]·9H2O (TBA-AlMo6-LA, where TBA = tetrabutylammonium), was prepared via two synthetic routes and characterized by thermogravimetric and elemental analyses, mass spectrometry, IR and 1H NMR spectroscopy, and powder and single-crystal X-ray diffraction. The interaction of TBA-AlMo6-LA with human serum albumin (HSA) was investigated via fluorescence and circular dichroism spectroscopy. The results revealed that TBA-AlMo6-LA binds strongly to HSA (63% quenching at an HSA/TBA-AlMo6-LA ratio of 1:1), exhibiting static quenching. In contrast to TBA-AlMo6-LA, the nonfunctionalized polyoxometalate, Na3(H2O)6[Al(OH)6Mo6O18]·2H2O (AlMo6), showed weak binding toward HSA (22% quenching at a HSA/AlMo6 ratio of 1:25). HSA binding was confirmed by X-ray structure analysis of the HSA-Myr-AlMo6-LA complex (Myr = myristate). These results provide a promising lead for the design of novel polyoxometalate-based hybrids that are able to exploit HSA as a delivery vehicle to improve their pharmacokinetics and bioactivity.

Bone impairment caused by AlCl3 is associated with activation of the JNK apoptotic pathway mediated by oxidative stress.

Exposure to aluminum (Al) inhibits bone formation, the principal mechanism possibly due to oxidative stress. However, little data is available that establishes the precise relationship. In this study, Wistar rats were exposed to 0 (GC), 0.4 (GL), 0.8 (GM) or 1.6 (GH) mg/L aluminum trichloride (AlCl3) in drinking water for 90 days, respectively. The concentrations of Al in serum and bone, serum markers of bone metabolism, bone mineral density (BMD) and body weight were measured. Histological changes within femurs were observed by H&E, ALP, and TRACP staining. Oxidative stress markers and JNK apoptotic pathway were detected in bone. The results indicate that AlCl3 exposure decreased BMD, numbers of ALP-positive osteoblasts and serum levels of bone formation markers (B-ALP, PICP and BGP), and caused damaged to the trabecular structure. Serum levels of bone resorption markers (TRACP-5b, CTX-I) and numbers of TRACP-positive osteoclasts increased in GL, but conversely, they decreased in GM and GH. In addition, AlCl3 caused oxidative stress, up-regulated expression of c-Jun and pro-apoptotic factors with increased p-JNK/JNK ratio and down-regulated expression of anti-apoptotic factor Bcl-2 in bone. Taken together, these results indicate that bone impairment caused by AlCl3 is associated with activation of the oxidative stress-mediated JNK apoptotic pathway.

Quantitative Analysis of Vaccine Antigen Adsorption to Aluminum Adjuvant Using an Automated High-Throughput Method.

Aluminum-containing adjuvants have been widely used in vaccine formulations to safely and effectively potentiate the immune response. The examination of the extent of antigen adsorption to aluminum adjuvant is always evaluated during the development of aluminum adjuvant containing vaccines. A rapid, automated, high-throughput assay was developed to measure antigen adsorption in a 96-well plate format using a TECAN Freedom EVO® (TECAN). The antigen adsorption levels at a constant adjuvant concentration for each sample were accurately measured at 12 antigen/adjuvant (w/w) formulation ratios. These measurements were done at aluminum adjuvant concentrations similar to normal vaccine formulations, unlike previous non-automated and automated adjuvant adsorption studies. Two high-sensitivity analytical methods were used to detect the non-absorbed antigens. The antigen-to-adjuvant adsorption curves were fit to a simple Langmuir adsorption model for quantitatively analyzing the antigen to the adjuvant adsorption level and strength. The interaction of two model antigens, bovine serum albumin and lysozyme, with three types of aluminum adjuvant, were quantitatively analyzed in this report. Automated, high-throughput methodologies combined with sensitive analytical methods are useful for accelerating practical vaccine formulation development.LAY ABSTRACT: Vaccines are probably the most effective public health method to prevent epidemics of many infectious diseases. Many of the most effective vaccines contain aluminum adjuvant. This report describes novel technology that can be used to better optimize the efficacy and stability of aluminum adjuvant-containing vaccines.

Critical analysis of reference studies on the toxicokinetics of aluminum-based adjuvants.

We reviewed the three toxicokinetic reference studies commonly used to suggest that aluminum (Al)-based adjuvants are innocuous. A single experimental study was carried out using isotopic 26Al (Flarend et al., Vaccine, 1997). This study used aluminum salts resembling those used in vaccines but ignored adjuvant uptake by cells that was not fully documented at the time. It was conducted over a short period of time (28days) and used only two rabbits per adjuvant. At the endpoint, Al elimination in the urine accounted for 6% for Al hydroxide and 22% for Al phosphate, both results being incompatible with rapid elimination of vaccine-derived Al in urine. Two theoretical studies have evaluated the potential risk of vaccine Al in infants, by reference to an oral "minimal risk level" (MRL) extrapolated from animal studies. Keith et al. (Vaccine, 2002) used a high MRL (2mg/kg/d), an erroneous model of 100% immediate absorption of vaccine Al, and did not consider renal and blood-brain barrier immaturity. Mitkus et al. (Vaccine, 2011) only considered solubilized Al, with erroneous calculations of absorption duration. Systemic Al particle diffusion and neuro-inflammatory potential were omitted. The MRL they used was both inappropriate (oral Al vs. injected adjuvant) and still too high (1mg/kg/d) regarding recent animal studies. Both paucity and serious weaknesses of reference studies strongly suggest that novel experimental studies of Al adjuvants toxicokinetics should be performed on the long-term, including both neonatal and adult exposures, to ensure their safety and restore population confidence in Al-containing vaccines.

Study of potential transfer of aluminum to the brain via the olfactory pathway.

Many employees in the aluminum industry are exposed to a range of aluminum compounds by inhalation, and the presence of ultrafine particles in the workplace has become a concern to occupational health professionals. Some metal salts and metal oxides have been shown to enter the brain through the olfactory route, bypassing the blood-brain barrier, but few studies have examined whether aluminum compounds also use this pathway. In this context, we sought to determine whether aluminum was found in rat olfactory bulbs and whether its transfer depended on physicochemical characteristics such as solubility and granulometry. Aluminum salts (chloride and fluoride) and various nanometric aluminum oxides (13nm, 20nm and 40-50nm) were administered to rats by intranasal instillation through one nostril (10µg Al/30µL for 10days). Olfactory bulbs (ipsilateral and contralateral relative to instilled nostril) were harvested and the aluminum content was determined by graphite furnace atomic absorption spectrometry after tissue mineralization. Some transfer of aluminum salts to the central nervous system via the olfactory route was observed, with the more soluble aluminum chloride being transferred at higher levels than aluminum fluoride. No cerebral translocation of any of the aluminas studied was detected.

Effects of aluminum chloride on serum proteins, bilirubin, and hepatic trace elements in chickens.

The aim of this study was to reveal the effects of aluminum chloride (AlCl3) on the hepatic metabolism function and trace elements' distribution. Two hundred healthy male chickens (1 day old) were intraperitoneally administered with AlCl3 (0, 18.31, 27.47, and 36.62 mg kg(-1) day(-1) of Al(3+)) consecutively for 3 days. Then the chickens were allowed to rest for 1 day. The cycle lasted four days. The cycle was repeated 15 times (60 days). The contents of serum total protein (TP), albumin (ALB), total bilirubin (TBI), direct bilirubin (DBI), hepatic aluminum (Al), copper (Cu), iron (Fe), and zinc (Zn) were examined. The results showed that the contents of serum TP and ALB and hepatic Fe and Zn decreased and the contents of serum TBI and DBI and hepatic Al and Cu increased in the chickens with AlCl3 This indicates that chronic administration of AlCl3 impairs the hepatic metabolism function and disorders the hepatic trace elements' distribution.

Aluminum trichloride impairs bone and downregulates Wnt/ß-catenin signaling pathway in young growing rats.

Aluminum (Al) can accumulate in bone and cause bone diseases. Few studies have investigated molecular mechanism of Al-induced bone diseases. Thus, in this study, rats were orally exposed to 0 (control group) and 0.4 g/L aluminum trichloride (AlCl3) (treatment group) for 30, 60, 90 or 120 days, respectively. The Al content of femora and serum, bone histological structure, bone mineral density (BMD) of the distal and proximal femoral metaphysis and Wnt/ß-catenin signaling pathway (the mRNA expressions of Wnt3a, Fzd2, LRP-5, ß-catenin, Tcf4, cyclin D1 and c-Myc, the protein levels of Wnt3a and ß-catenin, the activities of Fzd2 and LRP-5) in rat femora were determined on day 30, 60, 90 or 120, respectively. The results showed that the Al contents of femora and serum were increased, the BMD of the distal and proximal femoral metaphysis were decreased, the femora histological structure were disrupted, the mRNA expressions of Wnt3a, Fzd2, LRP-5, ß-catenin, Tcf4, cyclin D1 and c-Myc, the protein levels of Wnt3a and ß-catenin, the activities of Fzd2 and LRP-5 were all decreased in the treatment group compared with the control group with time prolonged. These results indicated that AlCl3 impaired femora by inhibiting the Wnt/ß-catenin signaling pathway in young growing rats.

Effect of lysine acetylsalicylate on aluminium accumulation and (Na(+)/K(+))ATPase activity in rat brain cortex synaptosomes after aluminium ingestion.

Aluminium is neurotoxic in humans and has been implicated in several neurological disorders. Chronic use of buffered aspirins, as aspegic, would likely constitute the major human aluminium uptake source. Low-dose aspirin is beneficial in secondary prevention of cardiovascular events, so it is widely used for long periods of time. We studied if oral administration of aspegic to rats modified the aluminium inhibitory effect on brain (Na(+)/K(+))ATPase due to alteration in synaptosomal membrane aluminium content. Adult male Wistar rats were submitted to sub-acute (1.00g/day during 10 days) and chronic (0.03g/day during 4 months) dietary AlCl3 exposure and/or to aspegic (0.11g/day). The exposure protocol increased the synaptosomal aluminium content especially after a long-term exposure to aluminium and aspegic. Although no alterations were observed in rat body weight gain and adenylate energy charge, the (Na(+)/K(+))ATPase activity was significantly reduced when aluminium was orally administered to rats. The oral administration of aspegic increased the synaptosomal aluminium content and concomitantly enhanced the (Na(+)/K(+))ATPase inhibition. In our exposure protocol the increase in synaptosomal aluminium content correlates with the reduction of the (Na(+)/K(+))ATPase activity.

Effects of subchronic aluminum exposure on spatial memory, ultrastructure and L-LTP of hippocampus in rats.

Epidemiological investigations have indicated that aluminum (Al), as an important environmental neurotoxicant, could cause damage to the cognitive function which was closely related with neurodegenerative diseases. Long-term potentiation (LTP) is one form of synaptic plasticity in association with cognitive function. Previous studies have demonstrated that Al impaired early phase long-term potentiation (E-LTP) in vivo and in vitro. However, Al-induced damage to late phase long-term potentiation (L-LTP) has poorly been studied. The present study was designed to observe the effects of subchronic Al exposure on the spatial memory, hippocampus ultrastructure and L-LTP in rats. Pregnant Wistar rats were assigned to four groups. Neonatal rats were exposed to Al by parental lactation from parturition to weaning for 3 weeks and then fed with the distilled water containing 0, 0.2%, 0.4% and 0.6% aluminum chloride (AlCl3) respectively from weaning to postnatal 3 months. The levels of Al in blood and hippocampus were quantitated by atomic absorption spectrophotometer. Morris water maze test was performed to study spatial memory. The induction and maintenance of L-LTP in area of Schaffer collateral- CA1 synapse was recorded by extracellular microelectrode recording technology in hippocampus of experimental rats. Hippocampus was collected for transmission electron microscopy observation. The results showed that the Al concentrations in blood and hippocampus of Al-exposed rats were higher than those of the control rats. Al could impair spatial memory ability of rats. Neuronal and synaptic ultrastructure from Al-exposed rats presented pathological changes; the incidence of L-LTP has a decrease trend while population spike (PS) amplitude was much smaller significantly stimulated by high-frequency stimulation (HFS) in Al-exposed rats. Our findings showed that Al exposure caused spatial memory damage, under which the neuronal and synaptic ultrastructure changes maybe were their morphological basis and the impaired L-LTP of hippocampus could be their electrophysiological basis.

Structure of ADP-aluminium fluoride-stabilized protochlorophyllide oxidoreductase complex.

Photosynthesis uses chlorophylls for the conversion of light into chemical energy, the driving force of life on Earth. During chlorophyll biosynthesis in photosynthetic bacteria, cyanobacteria, green algae and gymnosperms, dark-operative protochlorophyllide oxidoreductase (DPOR), a nitrogenase-like metalloenzyme, catalyzes the chemically challenging two-electron reduction of the fully conjugated ring system of protochlorophyllide a. The reduction of the C-17=C-18 double bond results in the characteristic ring architecture of all chlorophylls, thereby altering the absorption properties of the molecule and providing the basis for light-capturing and energy-transduction processes of photosynthesis. We report the X-ray crystallographic structure of the substrate-bound, ADP-aluminium fluoride-stabilized (ADP·AlF(3)-stabilized) transition state complex between the DPOR components L(2) and (NB)(2) from the marine cyanobacterium Prochlorococcus marinus. Our analysis permits a thorough investigation of the dynamic interplay between L(2) and (NB)(2). Upon complex formation, substantial ATP-dependent conformational rearrangements of L(2) trigger the protein-protein interactions with (NB)(2) as well as the electron transduction via redox-active [4Fe-4S] clusters. We also present the identification of artificial "small-molecule substrates" of DPOR in correlation with those of nitrogenase. The catalytic differences and similarities between DPOR and nitrogenase have broad implications for the energy transduction mechanism of related multiprotein complexes that are involved in the reduction of chemically stable double and/or triple bonds.

Quantitative analysis and comparison study of [18F]AlF-NOTA-PRGD2, [18F]FPPRGD2 and [68Ga]Ga-NOTA-PRGD2 using a reference tissue model.

With favorable pharmacokinetics and binding affinity for α(v)ß(3) integrin, (18)F-labeled dimeric cyclic RGD peptide ([(18)F]FPPRGD2) has been intensively used as a PET imaging probe for lesion detection and therapy response monitoring. A recently introduced kit formulation method, which uses an (18)F-fluoride-aluminum complex labeled RGD tracer ([(18)F]AlF-NOTA-PRGD2), provides a strategy for simplifying the labeling procedure to facilitate clinical translation. Meanwhile, an easy-to-prepare (68)Ga-labeled NOTA-PRGD2 has also been reported to have promising properties for imaging integrin α(v)ß(3). The purpose of this study is to quantitatively compare the pharmacokinetic parameters of [(18)F]FPPRGD2, [(18)F]AlF-NOTA-PRGD2, and [(68)Ga]Ga-NOTA-PRGD2. U87MG tumor-bearing mice underwent 60-min dynamic PET scans following the injection of three tracers. Kinetic parameters were calculated using Logan graphical analysis with reference tissue. Parametric maps were generated using voxel-level modeling. All three compounds showed high binding potential (Bp(ND) = k(3)/k(4)) in tumor voxels. [(18)F]AlF-NOTA-PRGD2 showed comparable Bp(ND) value (3.75±0.65) with those of [(18)F]FPPRGD2 (3.39±0.84) and [(68)Ga]Ga-NOTA-PRGD2 (3.09±0.21) (p>0.05). Little difference was found in volume of distribution (V(T)) among these three RGD tracers in tumor, liver and muscle. Parametric maps showed similar kinetic parameters for all three tracers. We also demonstrated that the impact of non-specific binding could be eliminated in the kinetic analysis. Consequently, kinetic parameter estimation showed more comparable results among groups than static image analysis. In conclusion, [(18)F]AlF-NOTA-PRGD2 and [(68)Ga]Ga-NOTA-PRGD2 have comparable pharmacokinetics and quantitative parameters compared to those of [(18)F]FPPRGD2. Despite the apparent difference in tumor uptake (%ID/g determined from static images) and clearance pattern, the actual specific binding component extrapolated from kinetic modeling appears to be comparable for all three dimeric RGD tracers.

Improved phosphorus acquisition by tobacco through transgenic expression of mitochondrial malate dehydrogenase from Penicillium oxalicum.

Phosphorus (P) is an essential nutrient for plant growth and development, but is generally unavailable and inaccessible in soil, since applied P is mostly fixed to aluminium (Al) and ferrum (Fe) in acidic soils and to calcium (Ca) in alkaline soils. Increased organic acid excretion is thought to be one mechanism by which plants use to enhance P uptake. In this study, we overexpressed a mitochondrial malate dehydrogenase (MDH) gene from the mycorrhizal fungi Penicillium oxalicum in tobacco. The MDH activity of transgenic lines was significantly increased compared to that of wild type. Malate content in root exudation of transgenic lines induced in response to P deficiency was 1.3- to 2.9-fold greater than that of wild type under the same condition. Among the transgenic lines that were selected for analysis, one line (M1) showed the highest level of MDH activity and malate exudate. M1 showed a significant increase in growth over wild type, with 149.0, 128.5, and 127.9% increases in biomass, when grown in Al-phosphate, Fe-phosphate, and Ca-phosphate media, respectively. M1 also had better P uptake compared to wild type, with total P content increased by 287.3, 243.5, and 223.4% when grown in Al-phosphate, Fe-phosphate, and Ca-phosphate media, respectively. To our knowledge, this is the first study on improving the ability of a plant to utilize P from Al-phosphate, Fe-phosphate, and Ca-phosphate by manipulating the organic acid metabolism of the plant through genetic engineering.

Specific cleavage of the DNase-I binding loop dramatically decreases the thermal stability of actin.

Differential scanning calorimetry was used to investigate the thermal unfolding of actin specifically cleaved within the DNaseI-binding loop between residues Met47-Gly48 or Gly42-Val43 by two bacterial proteases, subtilisin or ECP32/grimelysin (ECP), respectively. The results obtained show that both cleavages strongly decreased the thermal stability of monomeric actin with either ATP or ADP as a bound nucleotide. An even more pronounced difference in the thermal stability between the cleaved and intact actin was observed when both actins were polymerized into filaments. Similar to intact F-actin, both cleaved F-actins were significantly stabilized by phalloidin and aluminum fluoride; however, in all cases, the thermal stability of the cleaved F-actins was much lower than that of intact F-actin, and the stability of ECP-cleaved F-actin was lower than that of subtilisin-cleaved F-actin. These results confirm that the DNaseI-binding loop is involved in the stabilization of the actin structure, both in monomers and in the filament subunits, and suggest that the thermal stability of actin depends, at least partially, on the conformation of the nucleotide-binding cleft. Moreover, an additional destabilization of the unstable cleaved actin upon ATP/ADP replacement provides experimental evidence for the highly dynamic actin structure that cannot be simply open or closed, but rather should be considered as being able to adopt multiple conformations.

A high-throughput screen for alpha particle radiation protectants.

Alpha-particle-emitting elements are of increasing importance as environmental and occupational carcinogens, toxic components of radiation dispersal devices and accidents, and potent therapeutics in oncology. Alpha particle radiation differs from radiations of lower linear energy transfer in that it predominantly damages DNA via direct action. Because of this, radical scavengers effective for other radiations have had only limited effect in mitigating alpha particle toxicity. We describe here a simple assay and a pilot screen of 3,119 compounds in a high-throughput screen (HTS), using the alpha-particle-emitting isotope, ²²5Ac, for the discovery of compounds that might protect mammalian cells from alpha particles through novel mechanisms. The assay, which monitored the viability of a myeloid leukemic cell line upon alpha particle exposure, was robust and reproducible, yielding a Z' factor of 0.66 and a signal-to-noise ratio of nearly 10 to 1. Surprisingly, 1 compound emerged from this screen, epoxy-4,5-α-dihydroxysantonin (EDHS), that showed considerable protective activity. While the value of EDHS remains to be determined, its discovery is a proof of concept and validation of the utility of this HTS methodology. Further application of the described assay could yield compounds useful in minimizing the toxicity and carcinogenesis associated with alpha particle exposure.

Transition state analogue structures of human phosphoglycerate kinase establish the importance of charge balance in catalysis.

Transition state analogue (TSA) complexes formed by phosphoglycerate kinase (PGK) have been used to test the hypothesis that balancing of charge within the transition state dominates enzyme-catalyzed phosphoryl transfer. High-resolution structures of trifluoromagnesate (MgF(3)(-)) and tetrafluoroaluminate (AlF(4)(-)) complexes of PGK have been determined using X-ray crystallography and (19)F-based NMR methods, revealing the nature of the catalytically relevant state of this archetypal metabolic kinase. Importantly, the side chain of K219, which coordinates the alpha-phosphate group in previous ground state structures, is sequestered into coordinating the metal fluoride, thereby creating a charge environment complementary to the transferring phosphoryl group. In line with the dominance of charge balance in transition state organization, the substitution K219A induces a corresponding reduction in charge in the bound aluminum fluoride species, which changes to a trifluoroaluminate (AlF(3)(0)) complex. The AlF(3)(0) moiety retains the octahedral geometry observed within AlF(4)(-) TSA complexes, which endorses the proposal that some of the widely reported trigonal AlF(3)(0) complexes of phosphoryl transfer enzymes may have been misassigned and in reality contain MgF(3)(-).

The immunobiology of aluminium adjuvants: how do they really work?

Aluminium adjuvants potentiate the immune response, thereby ensuring the potency and efficacy of typically sparingly available antigen. Their concomitant critical importance in mass vaccination programmes may have prompted recent intense interest in understanding how they work and their safety. Progress in these areas is stymied, however, by a lack of accessible knowledge pertaining to the bioinorganic chemistry of aluminium adjuvants, and, consequently, the inappropriate application and interpretation of experimental models of their mode of action. The objective herein is, therefore, to identify the many ways that aluminium chemistry contributes to the wide and versatile armoury of its adjuvants, such that future research might be guided towards a fuller understanding of their role in human vaccinations.