Magnesium(II)-ATP Complexes in 1-Ethyl-3-Methylimidazolium Acetate Solutions Characterized by 31Mg β-Radiation-Detected NMR Spectroscopy

The complexation of MgII with adenosine 5′-triphosphate (ATP) is omnipresent in biochemical energy conversion, but is difficult to interrogate directly. Here we use the spin-urn:x-wiley:14337851:media:anie202207137:anie202207137-math-0001 β-emitter 31Mg to study MgII-ATP complexation in 1-ethyl-3-methylimidazolium acetate (EMIM-Ac) solutions using β-radiation-detected nuclear magnetic resonance (β-NMR). We demonstrate that (nuclear) spin-polarized 31Mg, following ion-implantation from an accelerator beamline into EMIM-Ac, binds to ATP within its radioactive lifetime before depolarizing. The evolution of the spectra with solute concentration indicates that the implanted 31Mg initially bind to the solvent acetate anions, whereafter they undergo dynamic exchange and form either a mono- (31Mg-ATP) or di-nuclear (31MgMg-ATP) complex. The chemical shift of 31Mg-ATP is observed up-field of 31MgMg-ATP, in accord with quantum chemical calculations. These observations constitute a crucial advance towards using β-NMR to probe chemistry and biochemistry in solution

Oligopeptide Sequences of the Metal Binding Domain of CueR Metalloregulatory Proteins as Candidates for Toxic Metal Ion Capture

Various toxic metal ion resistance systems operate from bacterial level up to higher plants and animals. In bacteria, metalloregulatory proteins are key factors in the control of metal ion level. Inspired by the metal binding domain of these highly sensitive metal ion sensor proteins we have designed artificial oligopeptides, containing two cysteine residues, and investigated their interaction with cadmium(II) and mercury(II) ions. The studied ligands bound both metal ions with a rather high stability. The composition and solution structure of the various metal ion complexes have been determined. The genetic code of one of the oligopeptide sequences has been introduced into E. coli BL21 cells and (over)produced in the form of a fusion protein. Preliminary investigation of the viability and potential metal ion accumulation of the modified bacteria, compared to control cells, in the presence of cadmium(II) and mercury(II) has also been performed

On the possible roles of N-terminal His-rich domains of Cu,Zn SODs of some Gram-negative bacteria

The Cu,Zn superoxide dismutases (Cu,Zn SOD) isolated from some Gram-negative bacteria possess a His-rich N-terminal metal binding extension. The N-terminal domain of Haemophilus ducreyi Cu,Zn SOD has been previously proposed to play a copper(II)-, and may be a zinc(II)- chaperoning role under metal ion starvation, and to behave as a temporary (low activity) superoxide dismutating center if copper(II) is available. The N-terminal extension of Cu,Zn SOD from Actinobacillus pleuropneumoniae starts with an analogous sequence (HxDHxH), but contains considerably fewer metal binding sites. In order to study the possibility of the generalization of the above mentioned functions over all Gram-negative bacteria possessing His-rich N-terminal extension, here we report thermodynamic and solution structural analysis of the copper(II) and zinc(II) complexes of a peptide corresponding to the first eight amino acids (HADHDHKK-NH2, L) of the enzyme isolated from A. pleuropneumoniae. In equimolar solutions of Cu(II)/Zn(II) and the peptide the MH2L complexes are dominant in the neutral pH-range. L has extraordinary copper(II) sequestering capacity (KD,Cu = 7.4×10–13 M at pH 7.4), which is provided only by non-amide (side chain) donors. The central ion in CuH2L is coordinated by four nitrogens {NH2,3Nim} in the equatorial plane. In ZnH2L the peptide binds to zinc(II) through a {NH2,2Nim,COO–} donor set, and its zinc binding affinity is relatively modest (KD,Zn = 4.8×10–7 M at pH 7.4). Consequently, the presented data do support a general chaperoning role of the N-terminal His-rich region of Gram-negative bacteria in copper(II) uptake, but do not confirm similar function for zinc(II). Interestingly, the complex CuH2L has very high SOD-like activity, which may further support the multifunctional role of the copper(II)-bound N-terminal His-rich domain of Cu,Zn SODs of Gram-negative bacteria. The proposed structure for the MH2L complexes have been verified by semiempirical quantum chemical calculations (PM6), too

Billion-Fold Enhancement in Sensitivity of Nuclear Magnetic Resonance Spectroscopy for Magnesium Ions in Solution

NMR spectroscopy is highly sensitive as compared to conventional NMR spectroscopy, and may be applied for several elements across the periodic table. β - NMR has previously been applied successfully in the fields of nuclear and solid state physics. In this work β - NMR is applied for the first time to record an NMR spectrum for a species in solution. 31 Mg β - NMR spectra are measured for as few as 10 7 magnesium ions in ionic liquid (EMIM - Ac) within minutes as a prototypical test case. Resonances are observed at 3882.9 kHz and 3887.2 kHz in an external field of 0.3 T. The key achievement of the current work is to demonstrate that β - NMR is applicable for analysis o f species in solution, and thus represents a novel spectroscopic technique in general chemistry and potentially in biochemistry