JMS Letters

Desorption/ionization on self-assembled monolayer surfaces (DIAMS) In mass spectrometry, the laser desorption/ionization (LDI) method refers to an overall process by which the energy absorption of a laser beam by a localized region of an irradiated surface leads to the emission of gaseous charged particles. The most important steps involve the rapid dissipation of energy followed by the vaporization of the analyte, which acquires translational energy. Therefore, the direct irradiation of a sample, which induces a very rapid local heating and the absorption in the UV or IR region by the analyte, reduces the ionization efficiency and activates the dissociation of weak bonds during the energy transfer. This constitutes a limitation of the LDI technique, since only fragmented ions are detected even in the case of small-molecule analysis. To circumvent this problem, Karas and Hillenkamp 1 and Tanaka 2 have developed the matrix assisted laser desorption/ionization (MALDI) technique. This method uses a photonabsorbing mediator, i.e. an aromatic matrix molecule, which is co-crystallized with the analyte. The analyte dispersion into the matrix crystals and the structure of the irradiated matrix crystal surface play a key role in the energy dissipation process. In order to overcome these limitations, free-matrix laser ablation/ionization methods have been proposed in the literature. The LDI on porous silicon (DIOS) technique was developed because of the structure of the surface, which in this case provides a scaffold for retaining solvent and analyte molecules, and the UV absorptivity of the substrate, which affords a conversion mode for the transfer of the photon energy to the translational energy, leads to the sample vaporization process. 7 The 'surface-assisted laser desorption/ionization' (SALDI) method uses a thin layer of activated carbon particles immobilized on an aluminum support. 8 In this case, the sample can be directly deposited on the surface plate. An alternative technique uses a suspension of a fine graphite powder or functionalized nanoparticles 9 in a solution of the analyte in an organic solvent. Peptides and organic compounds were then detected in DIOS and SALDI mass spectrometry as protonated molecules and/or as alkali metal adducts. 10, By analogy with the surface properties of a UV-absorbing semiconductor (such as porous silicon), and with regard to the analytical flexibility offered by the possibility of functionalization of activated surfaces, we propose here the use of some organic surfaces in the LDI techniques. This new free-matrix laser desorption ionization method developed is termed desorption/ionization on self-assembled monolayer surfaces (DIAMS) and uses self-assembled monolayers (SAMs). SAMs are defined as two-dimensional films, one molecule thick, covalently assembled at an interface. These organic assemblies result, in most cases, from the reaction in solution between the headgroup function of a molecular constituent and a metal, oxide or semiconductor surface. The synthesis of the SAMs precursor compounds starts from the 2-bromothiophene and is described in Scheme 1. Because of the propensity of the thiol function to oxidation, all characterizations in solution were carried out on the protected alkane-thiol (1). As expected from previous results reported in the literature, the characteristic optical band of 1 is observed at 340 nm

Desorption/Ionization on self-Assembled Monolayer Surface (DIAMS) Evaluation of a New Matrix-Free Laser Desorption/Ionization method

Date du colloque&nbsp;: 06/2008</p

A new prescription model for regional citrate anticoagulation in therapeutic plasma exchanges.

Regional citrate anticoagulation (RCA) is proposed for various extracorporeal purification techniques to overcome the risk of bleeding that might result from systemic anticoagulation. Yet, no individualized treatment protocol has been proposed for therapeutic plasma exchange (TPE) so far. The objective of this study was to assess the determinants of blood citrate concentration needed and to develop an individualized RCA protocol useful for clinical practice. The study population included 14 patients who underwent a total of 47 TPE sessions. Citrate was infused pre-plasmafilter. Post-plasmafilter and systemic plasma ionized calcium concentrations were measured at standardized time intervals. An algorithm was proposed for the supplementation of calcium. During the discovery phase, citrate was infused at a fixed starting rate, and adapted accordingly to obtained post-plasmafilter ionized calcium levels. Using a mathematical approach, an algorithm was thereafter developed for individualized prescriptions of citrate. Pre-treatment values of hematocrit and plasma ionized calcium were the main determinants of the required rate of citrate infusion. These can be integrated into a final equation enabling to individualize the prescription. A prefilter ionized calcium concentration between 0.24 and 0.33 mmol/l prevented coagulation of the extracorporeal circuit. Significant hypocalcemia occurred in 8.5% of treatments. There were no significant acid-base disturbances. We propose a new protocol, which enables for the first time to individualize the prescription of regional citrate anticoagulation during TPE, in an efficient manner. The immediately obtained regional anticoagulation protects against both the risk of coagulation of the membrane and the exposure to an excess of citrate

Erratum to: A new prescription model for regional citrate anticoagulation in therapeutic plasma exchanges.

BACKGROUND: Regional citrate anticoagulation (RCA) is proposed for various extracorporeal purification techniques to overcome the risk of bleeding that might result from systemic anticoagulation. Yet, no individualized treatment protocol has been proposed for therapeutic plasma exchange (TPE) so far. The objective of this study was to assess the determinants of blood citrate concentration needed and to develop an individualized RCA protocol useful for clinical practice. METHODS: The study population included 14 patients who underwent a total of 47 TPE sessions. Citrate was infused pre-plasmafilter. Post-plasmafilter and systemic plasma ionized calcium concentrations were measured at standardized time intervals. An algorithm was proposed for the supplementation of calcium. During the discovery phase, citrate was infused at a fixed starting rate, and adapted accordingly to obtained post-plasmafilter ionized calcium levels. Using a mathematical approach, an algorithm was thereafter developed for individualized prescriptions of citrate. RESULTS: Pre-treatment values of hematocrit and plasma ionized calcium were the main determinants of the required rate of citrate infusion. These can be integrated into a final equation enabling to individualize the prescription. A prefilter ionized calcium concentration between 0.24 and 0.33 mmol/l prevented coagulation of the extracorporeal circuit. Significant hypocalcemia occurred in 8.5% of treatments. There were no significant acid–base disturbances. CONCLUSION: We propose a new protocol, which enables for the first time to individualize the prescription of regional citrate anticoagulation during TPE, in an efficient manner. The immediately obtained regional anticoagulation protects against both the risk of coagulation of the membrane and the exposure to an excess of citrate. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12882-017-0494-9) contains supplementary material, which is available to authorized users

A promising method for efficient analysis of secondary metabolites in plant extracts by a matrix-free Desorption/Ionization on self-Assembled Monolayer Surfaces (DIAMS) technique

Plants are one of the major sources for the biologically active organic compounds and play a key role in medicinal chemistry for the treatment of various diseases [1]. DIAMS method is able to determine the secondary metabolites of complex vegetal extracts. The high throughput analyses of vegetal extracts are relatively difficult to perform in MALDI mass spectrometry, since the preparation of the sample involves the co-crystallization of the matrix with the analyte. Moreover irradiation of the matrix ion produces many low-m/z vs high-intensity ions preventing the detection of low molecular weight molecules such as secondary metabolites. We have developed a matrix-free alternative to MALDI analyses by the means of an original desorption/ionization on self-assembled monolayers surfaces (DIAMS) technique [2]. Monolayers were formed by using novel thiophene and coumarin-triazole analogues that absorbs the laser beam at 337nm. We herein disclose our findings with respect to the DIAMS method which is well suitable for the detection and quantification of the low molecular weight compounds that are present in plant extracts. Some of the isoquinoline alkaloids from the root extracts of Thalictrum flavum have been detected by the DIAMS method. Indeed, this technique would be promising suitable for the qualitative and quantitative analysis of polar and non-polar organic components that are widely distributed in the plants, without any preliminary chromatographic resolution [3]

Energy-oriented analysis of HPC Cluster Queues: Emerging Metrics for Sustainable Data Center

This work analyzes a very subtle kind of energy metrics for Data Centers (DCs), namely productivity metrics which affect the global energy efficiency assessment in DC since they focus on the energy used for processing computing operations. By exploiting the available set of energy consumption data of operating systems in ENEA-DC, HPC-Cluster, the authors evaluated the energy consumed by different queues with several running applications. The queues energy waste has been calculated to provide an assessment for the ineffective use of computation-related energy load within the Cluster. This work shows an increment innovation beyond state-of-the-art for productivity metrics (e.g. useful work), and it will also help provide an invaluable insight into useful energy use and the use of enhanced sustainability metrics with the goal of driving a more sustainable DC. Additionally, sustainability concept in DC operations is driven by estimation of its indirect carbon emissions, which is shown in this work

Separate and combined analysis of successive dependent outcomes after breast-conservation surgery: recurrence, metastases, second cancer and death

<p>Abstract</p> <p>Background</p> <p>In the setting of recurrent events, research studies commonly count only the first occurrence of an outcome in a subject. However this approach does not correctly reflect the natural history of the disease. The objective is to jointly identify prognostic factors associated with locoregional recurrences (LRR), contralateral breast cancer, distant metastases (DM), other primary cancer than breast and breast cancer death and to evaluate the correlation between these events.</p> <p>Methods</p> <p>Patients (n = 919) with a primary invasive breast cancer and treated in a cancer center in South-Western France with breast-conserving surgery from 1990 to 1994 and followed up to January 2006 were included. Several types of non-independent events could be observed for the same patient: a LRR, a contralateral breast cancer, DM, other primary cancer than breast and breast cancer death. Data were analyzed separately and together using a random-effects survival model.</p> <p>Results</p> <p>LRR represent the most frequent type of first failure (14.6%). The risk of any event is higher for young women (less than 40 years old) and in the first 10 years of follow-up after the surgery. In the combined analysis histological tumor size, grade, number of positive nodes, progesterone receptor status and treatment combination are prognostic factors of any event. The results show a significant dependence between these events with a successively increasing risk of a new event after the first and second event. The risk of developing a new failure is greatly increased (RR = 4.25; 95%CI: 2.51-7.21) after developing a LRR, but also after developing DM (RR = 3.94; 95%CI: 2.23-6.96) as compared to patients who did not develop a first event.</p> <p>Conclusion</p> <p>We illustrated that the random effects survival model is a more satisfactory method to evaluate the natural history of a disease with multiple type of events.</p

Evaluation of a new matrix-free laser desorption/ionization method through statistic studies: comparison of the DIAMS (desorption/ionization on self-assembled monolayer surface) method with the MALDI and TGFA-LDI techniques

This work demonstrates that the desorption/ionization on self-assembled monolayer surface (DIAMS) mass spectrometry, a recent matrix-free laser desorption/ionization (LDI) method based on an organic target plate, is as statistically repeatable and reproducible as matrix assisted laser desorption ionization (MALDI) and thin gold film-assisted laser desorption/ionization (TGFA-LDI) mass spectrometries. On lipophilic DIAMS of target plates with a mixture of glycerides, repeatability/reproducibility has been estimated at 15 and 30% and the relative detection limit has been evaluated at 0.3 and 3 pmol, with and without NaI respectively. Salicylic acid and its d6-isomer analysis confirm the applicability of the DIAMS method in the detection of compounds of low molecular weight