Diamidophosphate (DAP): A Plausible Prebiotic Phosphorylating Reagent with a Chem to BioChem Potential?

Known since the 1890s, diamidophosphate (DAP) has been investigated within the context of its inorganic chemistry. In 1999 - with the demonstration of DAP's potential as a phosphorylating agent of sugars in aqueous medium - began the exciting phase of research about DAP's role as a plausible prebiotic phosphorylating agent. More recently, in the last five years, there has been a steady increase in the publications that have documented the surprising versatility of DAP enabling the emergence of many classes of biomolecules of life, such as nucleic acids, peptides and protocells. Thus, though in its infancy, DAP seems to be uniquely positioned to play a central role in modelling abiotic- to prebiotic-chemical evolution. In this context, there is a need for systematic investigations for: (a) establishing DAP's likely availability on the early Earth, and (b) developing DAP's potential as a tool for use in synthetic and bioorganic chemistry.

Niche differentiation and plasticity in soil phosphorus acquisition among co-occurring plants.

How species coexist despite competing for the same resources that are in limited supply is central to our understanding of the controls on biodiversity1,2. Resource partitioning may facilitate coexistence, as co-occurring species use different sources of the same limiting resource3,4. In plant communities, however, direct evidence for partitioning of the commonly limiting nutrient, phosphorus (P), has remained scarce due to the challenges of quantifying P acquisition from its different chemical forms present in soil5. To address this, we used 33P to directly trace P uptake from DNA, orthophosphate and calcium phosphate into monocultures and mixed communities of plants growing in grassland soil. We show that co-occurring plants acquire P from these important organic and mineral sources in different proportions, and that differences in P source use are consistent with the species' root adaptations for P acquisition. Furthermore, the net benefit arising from niche plasticity (the gain in P uptake for a species in a mixed community compared to monoculture) correlates with species abundance in the wild, suggesting that niche plasticity for P is a driver of community structure. This evidence for P resource partitioning and niche plasticity may explain the high levels of biodiversity frequently found in P-limited ecosystems worldwide6,7.

Metabolic alterations provide insights into Stylosanthes roots responding to phosphorus deficiency.

BACKGROUND: Phosphorus (P) deficiency is one of the major constraints limiting plant growth, especially in acid soils. Stylosanthes (stylo) is a pioneer tropical legume with excellent adaptability to low P stress, but its underlying mechanisms remain largely unknown. RESULTS: In this study, the physiological, molecular and metabolic changes in stylo responding to phosphate (Pi) starvation were investigated. Under low P condition, the growth of stylo root was enhanced, which was attributed to the up-regulation of expansin genes participating in root growth. Metabolic profiling analysis showed that a total of 256 metabolites with differential accumulations were identified in stylo roots response to P deficiency, which mainly included flavonoids, sugars, nucleotides, amino acids, phenylpropanoids and phenylamides. P deficiency led to significant reduction in the accumulation of phosphorylated metabolites (e.g., P-containing sugars, nucleotides and cholines), suggesting that internal P utilization was enhanced in stylo roots subjected to low P stress. However, flavonoid metabolites, such as kaempferol, daidzein and their glycoside derivatives, were increased in P-deficient stylo roots. Furthermore, the qRT-PCR analysis showed that a set of genes involved in flavonoids synthesis were found to be up-regulated by Pi starvation in stylo roots. In addition, the abundances of phenolic acids and phenylamides were significantly increased in stylo roots during P deficiency. The increased accumulation of the metabolites in stylo roots, such as flavonoids, phenolic acids and phenylamides, might facilitate P solubilization and cooperate with beneficial microorganisms in rhizosphere, and thus contributing to P acquisition and utilization in stylo. CONCLUSIONS: These results suggest that stylo plants cope with P deficiency by modulating root morphology, scavenging internal Pi from phosphorylated metabolites and increasing accumulation of flavonoids, phenolic acids and phenylamides. This study provides valuable insights into the complex responses and adaptive mechanisms of stylo roots to P deficiency.

Functional identification of apple MdMYB2 gene in phosphate-starvation response.

Inorganic phosphate (Pi) starvation severely affects the normal growth and development of plants. Here, a Pi-responsive gene, named MdMYB2 (MDP0000823458), was cloned and functionally identified in apple. Overexpression of MdMYB2 regulated the expression of Pi starvation-induced (PSI) genes and then promoted phosphate assimilation and utilization. The ectopic expression of MdMYB2 in Arabidopsis influenced plant growth and flowering, which was partially rescued by application of exogenous gibberellin (GA). These results indicated that MdMYB2 may be an essential regulator in phosphate utilization and GA-regulated plant growth and development.

Bioinspired Thiophosphorodichloridate Reagents for Chemoselective Histidine Bioconjugation.

Site-selective bioconjugation to native protein residues is a powerful tool for protein functionalization, with cysteine and lysine side chains being the most common points for attachment owing to their high nucleophilicity. We now report a strategy for histidine modification using thiophosphorodichloridate reagents that mimic post-translational histidine phosphorylation, enabling fast and selective labeling of protein histidines under mild conditions where various payloads can be introduced via copper-assisted alkyne-azide cycloaddition (CuAAC) chemistry. We establish that these reagents are particularly effective at covalent modification of His-tags, which are common motifs to facilitate protein purification, as illustrated by selective attachment of polyarginine cargoes to enhance the uptake of proteins into living cells. This work provides a starting point for probing and enhancing protein function using histidine-directed chemistry.

The arbuscular mycorrhizal fungus Rhizophagus irregularis MUCL 41833 increases the phosphorus uptake and biomass of Medicago truncatula, a benzo[a]pyrene-tolerant plant species.

The accumulation of phosphorus (P) in plants increases their biomass and resistance/tolerance to organic pollutants. Both characteristics are mandatory for the utilization of plants in phytoremediation. Arbuscular mycorrhizal (AM) fungi improve plant P nutrition, and thus growth. However, only a few studies have focused on the dynamics of inorganic P (Pi) uptake in AM fungal-colonized plants in the presence of organic pollutants. Indeed, most of the results so far were obtained after harvesting the plants, thus by evaluating P concentration and content at a single time point. Here, we investigated the effects of the AM fungus Rhizophagus irregularis MUCL 41833 on the short-term Pi uptake dynamics of Medicago truncatula plants grown in the presence of benzo[a]pyrene (B[a]P), a polyaromatic hydrocarbon (PAH) frequently found in polluted soils. The study was conducted using a non-destructive circulatory semi-hydroponic cultivation system to investigate the short-term Pi depletion from a nutrient solution and as a corollary, the Pi uptake by the AM fungal-colonized and non-colonized plants. The growth, P concentration, and content of plants were also evaluated at harvest. The presence of B[a]P neither impacted the development of the AM fungus in the roots nor the plant growth and Pi uptake, suggesting a marked tolerance of both organisms to B[a]P pollution. A generally higher Pi uptake coupled with a higher accumulation of P in shoots and roots was noticed in AM fungal-colonized plants as compared to the non-colonized controls, irrespective of the presence or absence of B[a]P. Therefore, fungal-colonized plants showed the best growth. Furthermore, the beneficial effect provided by the presence of the AM fungus in roots was similar in presence or absence of B[a]P, thus opening the door for potential utilization in phytomanagement of PAH-polluted soils.

Eight Kinetically Stable but Thermodynamically Activated Molecules that Power Cell Metabolism.

Contemporary analyses of cell metabolism have called out three metabolites: ATP, NADH, and acetyl-CoA, as sentinel molecules whose accumulation represent much of the purpose of the catabolic arms of metabolism and then drive many anabolic pathways. Such analyses largely leave out how and why ATP, NADH, and acetyl-CoA (Figure 1 ) at the molecular level play such central roles. Yet, without those insights into why cells accumulate them and how the enabling properties of these key metabolites power much of cell metabolism, the underlying molecular logic remains mysterious. Four other metabolites, S-adenosylmethionine, carbamoyl phosphate, UDP-glucose, and Δ2-isopentenyl-PP play similar roles in using group transfer chemistry to drive otherwise unfavorable biosynthetic equilibria. This review provides the underlying chemical logic to remind how these seven key molecules function as mobile packets of cellular currencies for phosphoryl transfers (ATP), acyl transfers (acetyl-CoA, carbamoyl-P), methyl transfers (SAM), prenyl transfers (IPP), glucosyl transfers (UDP-glucose), and electron and ADP-ribosyl transfers (NAD(P)H/NAD(P)+) to drive metabolic transformations in and across most primary pathways. The eighth key metabolite is molecular oxygen (O2), thermodynamically activated for reduction by one electron path, leaving it kinetically stable to the vast majority of organic cellular metabolites.

Genetically encoded sensors for monitoring the transport and concentration of nitrogen-containing and phosphorus-containing molecules in plants.

Nitrogen and phosphorus are macronutrients indispensable for plant growth. The acquisition and reallocation of both elements require a multitude of dedicated transporters that specifically recognize inorganic and organic forms of nitrogen and phosphorous. Although many transporters have been discovered through elegant screening processes and sequence homology, many remain uncharacterized for their functions in planta. Genetically encoded sensors for nitrogen and phosphorous molecules offer a unique opportunity for studying transport mechanisms that were previously inaccessible. In the past few years, sensors for some of the key nitrogen molecules became available, and many improvements have been made for existing sensors for phosphorus molecules. Methodologies for detailed in vivo analysis also improved. We summarize the recent improvements in genetically encoded sensors for nitrogen and phosphorus molecules, and the discoveries made by using such sensors.

Biocatalytic Phosphorylations of Metabolites: Past, Present, and Future.

Phosphorus is a key element for life that occurs in living cells as a structural part of many key biochemicals. Phosphorus plays important functional roles in biocatalysis, such as making metabolic reaction steps irreversible by transferring energy-rich groups, using phosphate groups as leaving groups, or selectively hydrolyzing phosphorus-oxygen or phosphorus-nitrogen bonds. The large number of biocatalysts known to catalyze the transfer of phosphorus-containing groups from donor molecules to acceptor molecules covers a wide variety of reaction classes. Bioprocessing technology can and should replicate these naturally occurring reactions. We illuminate some strategic advantages of this promising technology for developing biocatalytic processes and separation steps. Constraints, opportunities, and outlooks for implementing green engineering procedures to establish sustainable production processes are discussed.

Effects of sodium, 1,25-dihydroxyvitamin D3 and parathyroid hormone fragment on inorganic P absorption and Type IIb sodium-phosphate cotransporter expression in ligated duodenal loops of broilers.

Three experiments were conducted with 22-day-old Arbor Acres male broilers to study the effects of Na+, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and parathyroid hormone fragment [PTH (1-34)] on inorganic P absorption and Type IIb sodium-phosphate cotransporter (NaP-IIb) mRNA and protein expression levels in ligated duodenal loops. The duodenal loops were perfused with solutions (pH = 6) containing zero, 50, or 150 mmol/L of Na+ as NaCl in Exp. 1, containing zero, 30, or 300 pmol/L of 1,25-(OH)2D3 in Exp. 2, or containing zero, 65, or 650 pmol/L of PTH (1-34) in Exp. 3, respectively. Compared with the control, additions of 50 and 150 mmol/L of Na+, 30 and 300 pmol/L of 1,25-(OH)2D3, or 65 and 650 pmol/L of PTH (1-34) to the perfusates promoted (P < 0.02) the P absorption percentages and rates, respectively. Additions of the above-mentioned concentrations of Na+ or 1,25-(OH)2D3 to the perfusates increased (P < 0.003) NaP-IIb mRNA level in the duodenum of broilers, and a similar trend (P = 0.08) was observed for PTH (1-34). The Na+, 1,25-(OH)2D3, and PTH (1-34) had no effects (P > 0.15) on NaP-IIb protein level in the duodenum of broilers. The results indicate that increased P absorption due to perfusions of Na+, 1,25-(OH)2D3 or PTH (1-34) might be attributed to enhanced NaP-IIb expression in the duodenum of broilers.

Interleaved multivoxel 31 P MR spectroscopy.

PURPOSE: Separate measurements are required when investigating multiple exercising muscles with singlevoxel-localized dynamic 31 P-MRS. With multivoxel spectroscopy, 31 P-MRS time-series spectra are acquired from multiple independent regions during one exercise-recovery experiment with the same time resolution as for singlevoxel measurements. METHODS: Multiple independently selected volumes were localized using temporally interleaved semi-LASER excitations at 7T. Signal loss caused by mutual saturation from shared excitation or refocusing slices was quantified at partial and full overlap, and potential contamination was investigated in phantom measurements. During an exercise-recovery experiment both gastrocnemius medialis and soleus of two healthy volunteers were measured using multivoxel acquisitions with a total TR of 6 s, while avoiding overlap of excitation slices. RESULTS: Signal reduction by shared adiabatic refocusing slices selected 1 s after the preceding voxel was between 10% (full overlap) and 20% (half overlap), in a phantom measurement. In vivo data were acquired from both muscles within the same exercise experiment, with 13-18% signal reduction. Spectra show phosphocreatine, inorganic phosphate, adenosine-triposphate, phosphomonoesters, and phosphodiesters. CONCLUSION: Signal decrease was relatively low compared to the 2-fold increase in information. The approach could help to improve the understanding in metabolic research and is applicable to other organs and nuclei. Magn Reson Med 77:921-927, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Phylotype Dynamics of Bacterial P Utilization Genes in Microbialites and Bacterioplankton of a Monomictic Endorheic Lake.

Microbes can modulate ecosystem function since they harbor a vast genetic potential for biogeochemical cycling. The spatial and temporal dynamics of this genetic diversity should be acknowledged to establish a link between ecosystem function and community structure. In this study, we analyzed the genetic diversity of bacterial phosphorus utilization genes in two microbial assemblages, microbialites and bacterioplankton of Lake Alchichica, a semiclosed (i.e., endorheic) system with marked seasonality that varies in nutrient conditions, temperature, dissolved oxygen, and water column stability. We focused on dissolved organic phosphorus (DOP) utilization gene dynamics during contrasting mixing and stratification periods. Bacterial alkaline phosphatases (phoX and phoD) and alkaline beta-propeller phytases (bpp) were surveyed. DOP utilization genes showed different dynamics evidenced by a marked change within an intra-annual period and a differential circadian pattern of expression. Although Lake Alchichica is a semiclosed system, this dynamic turnover of phylotypes (from lake circulation to stratification) points to a different potential of DOP utilization by the microbial communities within periods. DOP utilization gene dynamics was different among genetic markers and among assemblages (microbialite vs. bacterioplankton). As estimated by the system's P mass balance, P inputs and outputs were similar in magnitude (difference was <10 %). A theoretical estimation of water column P monoesters was used to calculate the potential P fraction that can be remineralized on an annual basis. Overall, bacterial groups including Proteobacteria (Alpha and Gamma) and Bacteroidetes seem to be key participants in DOP utilization responses.

Considerations in applying compressed sensing to in vivo phosphorus MR spectroscopic imaging of human brain at 3T.

The purpose of this study was to apply compressed sensing method for accelerated phosphorus MR spectroscopic imaging (31P-MRSI) of human brain in vivo at 3T. Fast 31P-MRSI data of five volunteers were acquired on a 3T clinical MR scanner using pulse-acquire sequence with a pseudorandom undersampling pattern for a data reduction factor of 5.33 and were reconstructed using compressed sensing. Additionally, simulated 31P-MRSI human brain tumor datasets were created to analyze the effects of k-space sampling pattern, data matrix size, regularization parameters of the reconstruction, and noise on the compressed sensing accelerated 31P-MRSI data. The 31P metabolite peak ratios of the full and compressed sensing accelerated datasets of healthy volunteers in vivo were similar according to the results of a Bland-Altman test. The estimated effective spatial resolution increased with reduction factor and sampling more at the k-space center. A lower regularization parameter for both total variation and L1-norm penalties resulted in a better compressed sensing reconstruction of 31P-MRSI. Although the root-mean-square error increased with noise levels, the compressed sensing reconstruction was robust for up to a reduction factor of 10 for the simulated data that had sharply defined tumor borders. As a result, compressed sensing was successfully applied to accelerate 31P-MRSI of human brain in vivo at 3T.

Proton and phosphorus magnetic resonance spectroscopy of the healthy human breast at 7 T.

In vivo water- and fat-suppressed 1 H magnetic resonance spectroscopy (MRS) and 31 P magnetic resonance adiabatic multi-echo spectroscopic imaging were performed at 7 T in duplicate in healthy fibroglandular breast tissue of a group of eight volunteers. The transverse relaxation times of 31 P metabolites were determined, and the reproducibility of 1 H and 31 P MRS was investigated. The transverse relaxation times for phosphoethanolamine (PE) and phosphocholine (PC) were fitted bi-exponentially, with an added short T2 component of 20 ms for adenosine monophosphate, resulting in values of 199 ± 8 and 239 ± 14 ms, respectively. The transverse relaxation time for glycerophosphocholine (GPC) was also fitted bi-exponentially, with an added short T2 component of 20 ms for glycerophosphatidylethanolamine, which resonates at a similar frequency, resulting in a value of 177 ± 6 ms. Transverse relaxation times for inorganic phosphate, γ-ATP and glycerophosphatidylcholine mobile phospholipid were fitted mono-exponentially, resulting in values of 180 ± 4, 19 ± 3 and 20 ± 4 ms, respectively. Coefficients of variation for the duplicate determinations of 1 H total choline (tChol) and the 31 P metabolites were calculated for the group of volunteers. The reproducibility of inorganic phosphate, the sum of phosphomonoesters and the sum of phosphodiesters with 31 P MRS imaging was superior to the reproducibility of 1 H MRS for tChol. 1 H and 31 P data were combined to calculate estimates of the absolute concentrations of PC, GPC and PE in healthy fibroglandular tissue, resulting in upper limits of 0.1, 0.1 and 0.2 mmol/kg of tissue, respectively.

Whole-cell Proteus mirabilis urease inhibition by aminophosphinates for the control of struvite formation.

The study evaluated the in vitro impact of a series of aminophosphinic urease inhibitors on Proteusmirabilis. The group of compounds comprised structurally diverse analogues of diamidophosphate built on an N-C-P scaffold. The influence of urease inhibition on urea-splitting activity was assessed by whole-cell pH-static kinetic measurements. The potential to prevent struvite formation was determined by monitoring changes in pH and ionic composition of artificial urine medium during P. mirabilis growth. The most active compounds exhibited stronger positive effect on urine stability than the acknowledged inhibitor acetohydroxamic acid. The high anti-ureolytic and pH-stabilizing effect of urease inhibitors 4 and 14 was well correlated with their reported kinetic properties against pure urease from P. mirabilis (Ki values of 0.62±0.09 and 0.202±0.057 µM, respectively, compared to 5.7±0.4 µM for acetohydroxamic acid). The effect of repressed ureolysis upon the viability of Proteus cells was studied using MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide] metabolic efficiency assay and LIVE/DEAD fluorescent staining. Most of the compounds caused whole-cell dehydrogenase activity loss; four structures (1, 2, 4 and 14) reduced the culture viability by nearly 70 % at 1 mM concentration. Results of dual fluorescent staining suggested that besides urea-splitting prevention, the structures additionally exerted an outer-membrane-destabilizing effect.

The reproducibility of different metabolic markers for muscle fiber type distributions investigated by functional 31P-MRS during dynamic exercise.

PURPOSE: The objective of the study was to investigate the reproducibility of exercise induced pH-heterogeneity by splitting of the inorganic phosphate (Pi) signal in the corresponding 31P-MRS spectra and to compare results of this approach with other fiber-type related markers, like phosphocreatine/adenosine triphosphate (PCr/ATP) ratio, and PCr-recovery parameters. MATERIAL AND METHODS: Subjects (N=3) with different sportive background were tested in 10 test sessions separated by at least 3 days. A MR-compatible pedal ergometer was used to perform the exercise and to induce a pH-based splitting of the Pi-signal in 31P-MR spectra of the medial gastrocnemius muscle. The PCr recovery was analyzed using a non-negative least square algorithm (NNLS) and multi-exponential regression analysis to estimate the number of non-exponential components as well as their amplitude and time constant. The reproducibility of the estimated metabolic marker and the resulting fiber-type distributions between the 10 test sessions were compared. RESULTS: The reproducibility (standard deviation between measurements) based on (1) Pi components varied from 2% to 4%, (2) PCr recovery time components varied from 10% to 12% and (3) phosphate concentrations at rest varied from 8% to 11% between test sessions. Due to the sportive activity differences between the 3 subjects were expected in view of fiber type distribution. All estimated markers indicate the highest type I percentage for volunteer 3 medium for volunteer 2 and the lowest for volunteer 1. CONCLUSIONS: The relative high reproducibility of pH dependent Pi components during exercise indicates a high potential of this method to estimate muscle fiber-type distributions in vivo. To make this method usable not only to detect differences in muscle fiber distributions but also to determine individual fiber-type volume contents it is therefore recommended to validate this marker by histological methods and to reveal the effects of muscle fiber recruitments and fiber-type specific Pi concentrations on the intensity ratios between the splitted Pi-components.

Whole-body radiofrequency coil for (31) P MRSI at 7 T.

Widespread use of ultrahigh-field (31) P MRSI in clinical studies is hindered by the limited field of view and non-uniform radiofrequency (RF) field obtained from surface transceivers. The non-uniform RF field necessitates the use of high specific absorption rate (SAR)-demanding adiabatic RF pulses, limiting the signal-to-noise ratio (SNR) per unit of time. Here, we demonstrate the feasibility of using a body-sized volume RF coil at 7 T, which enables uniform excitation and ultrafast power calibration by pick-up probes. The performance of the body coil is examined by bench tests, and phantom and in vivo measurements in a 7-T MRI scanner. The accuracy of power calibration with pick-up probes is analyzed at a clinical 3-T MR system with a close to identical (1) H body coil integrated at the MR system. Finally, we demonstrate high-quality three-dimensional (31) P MRSI of the human body at 7 T within 5 min of data acquisition that includes RF power calibration. Copyright © 2016 John Wiley & Sons, Ltd.

Maternal Mineral and Bone Metabolism During Pregnancy, Lactation, and Post-Weaning Recovery.

During pregnancy and lactation, female physiology adapts to meet the added nutritional demands of fetuses and neonates. An average full-term fetus contains ∼30 g calcium, 20 g phosphorus, and 0.8 g magnesium. About 80% of mineral is accreted during the third trimester; calcium transfers at 300-350 mg/day during the final 6 wk. The neonate requires 200 mg calcium daily from milk during the first 6 mo, and 120 mg calcium from milk during the second 6 mo (additional calcium comes from solid foods). Calcium transfers can be more than double and triple these values, respectively, in women who nurse twins and triplets. About 25% of dietary calcium is normally absorbed in healthy adults. Average maternal calcium intakes in American and Canadian women are insufficient to meet the fetal and neonatal calcium requirements if normal efficiency of intestinal calcium absorption is relied upon. However, several adaptations are invoked to meet the fetal and neonatal demands for mineral without requiring increased intakes by the mother. During pregnancy the efficiency of intestinal calcium absorption doubles, whereas during lactation the maternal skeleton is resorbed to provide calcium for milk. This review addresses our current knowledge regarding maternal adaptations in mineral and skeletal homeostasis that occur during pregnancy, lactation, and post-weaning recovery. Also considered are the impacts that these adaptations have on biochemical and hormonal parameters of mineral homeostasis, the consequences for long-term skeletal health, and the presentation and management of disorders of mineral and bone metabolism.

2D AMESING multi-echo (31)P-MRSI of the liver at 7T allows transverse relaxation assessment and T2-weighted averaging for improved SNR.

PURPOSE: Liver diseases are a major global health concern often requiring invasive assessment by needle biopsy. (31)P magnetic resonance spectroscopic imaging (MRSI) allows non-invasive probing of important liver metabolites. Recently, the adiabatic multi-echo spectroscopic imaging sequence with spherical k-space sampling (AMESING) was introduced at 7T, enabling acquisition of T2 information. T2-weighed averaging of the multiple echoes improves signal-to-noise ratio (SNR). The purpose of our study was to implement AMESING MRSI of the liver at 3T and 7T, derive localized T2 information and compare T2-weighted average spectra in terms of SNR. METHODS: Ten male volunteers underwent 2D AMESING MRSI at 3T and 7T after a minimum four-hour fast. SNR was calculated for PC, PE, Pi, GPE, GPC and α-ATP using maximum peak amplitudes and the SD of the noise. Metabolite peak ratios were calculated after fitting in jMRUI. SNR values and peak ratios were compared with the Wilcoxon signed-rank test. RESULTS: For the first time liver metabolites' T2 values at 7T were measured: PE (55.6±3.5 ms), PC (51.2±2.3 ms), Pi (46.4±1.1 ms), GPE (44.0±0.8 ms), GPC (50.4±0.8 ms) and α-ATP (18.2±0.4 ms). SNR gain using T2-weighted averaging at 7T resulted in a 1.2× SNR gain. In conjunction with higher field strength and improved coil set-up T2-weighted averaging at 7T allowed a total 3.2× SNR gain compared to 3T FID-only. CONCLUSION: AMESING 2D MRSI of the liver at 7T provides T2 values that allow T2-weighted averaging of data from multiple echoes resulting in improved SNR.

Saturation-transfer effects and longitudinal relaxation times of (31) P metabolites in fibroglandular breast tissue at 7T.

PURPOSE: To investigate longitudinal relaxation times and saturation-transfer effects of phosphorous metabolites in breast fibroglandular tissue in vivo with (31) P MR spectroscopy at 7T. METHODS: Progressive saturation with adiabatic half passage excitation was used to determine T1 values of (31) P metabolites in a group of six healthy volunteers. Saturation-transfer experiments were performed in seven healthy volunteers by saturating at 0 ppm and 10 ppm with sinc-Gaussian pulses (90 ms; 10-ms pulse interval; B1 = 17 µT) prior to excitation. Localization was performed by surface coils and one-dimensional chemical shift imaging. Data were analyzed via spectral fitting with the JMRUI software package, and T1 values were obtained by fitting the data to the signal equation. RESULTS: The determined longitudinal relaxation time values at 7T were as follows: phosphoethanolamine, 4.0 ± 0.2 s; phosphocholine, 1.8 ± 0.2 s; inorganic phosphate, 6.1 ± 0.1 s; phosphodiesters, glycerophosphatidylethanolamine plus glycerophosphocholine, 2.1 ± 0.1, and glycerophosphatidylethanolamine, 1.5 ± 0.1s; γ-ATP, 2.1 ± 0.1 s; and α-ATP, 2.0 ± 0.1 s. Saturation-transfer measurements with saturation pulses at 0 ppm showed a significant signal reduction in the phosphodiester 2-3 ppm range, whereas the γ-ATP signal at -2.5 ppm was not affected significantly. CONCLUSION: Longitudinal relaxation times of phosphorous metabolites in fibroglandular tissue revealed relatively low T1 values for phosphodiesters. Saturation-transfer measurements showed that the phosphodiester signals were the only signals that were affected significantly, possibly indicating the presence of mobile phospholipids. Magn Reson Med 76:402-407, 2016. © 2015 Wiley Periodicals, Inc.