Commentary on Urinary l-erythro-ß-hydroxyasparagine: a novel serine racemase inhibitor and substrate of the Zn2+-dependent d-serine dehydratase.

The analysis of the urine contents can be informative of physiological homoeostasis, and it has been speculated that the levels of urinary d-serine (d-ser) could inform about neurological and renal disorders. By analysing the levels of urinary d-ser using a d-ser dehydratase (DSD) enzyme, Ito et al. (Biosci. Rep.(2021) 41, BSR20210260) have described abundant levels of l-erythro-ß-hydroxyasparagine (l-ß-EHAsn), a non-proteogenic amino acid which is also a newly described substrate for DSD. The data presented support the endogenous production l-ß-EHAsn, with its concentration significantly correlating with the concentration of creatinine in urine. Taken together, these results could raise speculations that l-ß-EHAsn might have unexplored important biological roles. It has been demonstrated that l-ß-EHAsn also inhibits serine racemase with Ki values (40 µM) similar to its concentration in urine (50 µM). Given that serine racemase is the enzyme involved in the synthesis of d-ser, and l-ß-EHAsn is also a substrate for DSD, further investigations could verify if this amino acid would be involved in the metabolic regulation of pathways involving d-ser.

Glycoprotein Semisynthesis by Chemical Insertion of Glycosyl Asparagine Using a Bifunctional Thioacid-Mediated Strategy.

Glycosylation is a major modification of secreted and cell surface proteins, and the resultant glycans show considerable heterogeneity in their structures. To understand the biological processes arising from each glycoform, the preparation of homogeneous glycoproteins is essential for extensive biological experiments. To establish a more robust and rapid synthetic route for the synthesis of homogeneous glycoproteins, we studied several key reactions based on amino thioacids. We found that diacyl disulfide coupling (DDC) formed with glycosyl asparagine thioacid and peptide thioacid yielded glycopeptides. This efficient coupling reaction enabled us to develop a new glycoprotein synthesis method, such as the bifunctional thioacid-mediated strategy, which can couple two peptides with the N- and C-termini of glycosyl asparagine thioacid. Previous glycoprotein synthesis methods required valuable glycosyl asparagine in the early stage and subsequent multiple glycoprotein synthesis routes, whereas the developed concept can generate glycoproteins within a few steps from peptide and glycosyl asparagine thioacid. Herein, we report the characterization of the DDC of amino thioacids and the efficient ability of glycosyl asparagine thioacid to be used for robust glycoprotein semisynthesis.

Urinary l-erythro-ß-hydroxyasparagine-a novel serine racemase inhibitor and substrate of the Zn2+-dependent d-serine dehydratase.

In the present study, we identified l-erythro-ß-hydroxyasparagine (l-ß-EHAsn) found abundantly in human urine, as a novel substrate of Zn2+-dependent d-serine dehydratase (DSD). l-ß-EHAsn is an atypical amino acid present in large amounts in urine but rarely detected in serum or most organs/tissues examined. Quantitative analyses of urinary l-ß-EHAsn in young healthy volunteers revealed significant correlation between urinary l-ß-EHAsn concentration and creatinine level. Further, for in-depth analyses of l-ß-EHAsn, we developed a simple three-step synthetic method using trans-epoxysuccinic acid as the starting substance. In addition, our research revealed a strong inhibitory effect of l-ß-EHAsn on mammalian serine racemase, responsible for producing d-serine, a co-agonist of the N-methyl-d-aspartate (NMDA) receptor involved in glutamatergic neurotransmission.

Cystobactamid 507: Concise Synthesis, Mode of Action, and Optimization toward More Potent Antibiotics.

Lack of new antibiotics and increasing antimicrobial resistance are among the main concerns of healthcare communities nowadays, and these concerns necessitate the search for novel antibacterial agents. Recently, we discovered the cystobactamids-a novel natural class of antibiotics with broad-spectrum antibacterial activity. In this work, we describe 1) a concise total synthesis of cystobactamid 507, 2) the identification of the bioactive conformation using noncovalently bonded rigid analogues, and 3) the first structure-activity relationship (SAR) study for cystobactamid 507 leading to new analogues with high metabolic stability, superior topoisomerase IIA inhibition, antibacterial activity and, importantly, stability toward the resistant factor AlbD. Deeper insight into the mode of action revealed that the cystobactamids employ DNA minor-groove binding as part of the drug-target interaction without showing significant intercalation. By designing a new analogue of cystobactamid 919-2, we finally demonstrated that these findings could be further exploited to obtain more potent hexapeptides against Gram-negative bacteria.

Unique Microbial Catabolic Pathway for the Human Core N-Glycan Constituent Fucosyl-α-1,6-N-Acetylglucosamine-Asparagine.

The survival of commensal bacteria in the human gut partially depends on their ability to metabolize host-derived molecules. The use of the glycosidic moiety of N-glycoproteins by bacteria has been reported, but the role of N-glycopeptides or glycoamino acids as the substrates for bacterial growth has not been evaluated. We have identified in Lactobacillus casei strain BL23 a gene cluster (alf-2) involved in the catabolism of the glycoamino acid fucosyl-α-1,6-N-GlcNAc-Asn (6'FN-Asn), a constituent of the core-fucosylated structures of mammalian N-glycoproteins. The cluster consists of the genes alfHC, encoding a major facilitator superfamily (MFS) permease and the α-l-fucosidase AlfC, and the divergently oriented asdA (aspartate 4-decarboxylase), alfR2 (transcriptional regulator), pepV (peptidase), asnA2 (glycosyl-asparaginase), and sugK (sugar kinase) genes. Knockout mutants showed that alfH, alfC, asdA, asnA2, and sugK are necessary for efficient 6'FN-Asn utilization. The alf-2 genes are induced by 6'FN-Asn, but not by its glycan moiety, via the AlfR2 regulator. The constitutive expression of alf-2 genes in an alfR2 strain allowed the metabolism of a variety of 6'-fucosyl-glycans. However, GlcNAc-Asn did not support growth in this mutant background, indicating that the presence of a 6'-fucose moiety is crucial for substrate transport via AlfH. Within bacteria, 6'FN-Asn is defucosylated by AlfC, generating GlcNAc-Asn. This glycoamino acid is processed by the glycosylasparaginase AsnA2. GlcNAc-Asn hydrolysis generates aspartate and GlcNAc, which is used as a fermentable source by L.casei These data establish the existence in a commensal bacterial species of an exclusive metabolic pathway likely to scavenge human milk and mucosal fucosylated N-glycopeptides in the gastrointestinal tract.IMPORTANCE The gastrointestinal tract accommodates more than 1014 microorganisms that have an enormous impact on human health. The mechanisms enabling commensal bacteria and administered probiotics to colonize the gut remain largely unknown. The ability to utilize host-derived carbon and energy resources available at the mucosal surfaces may provide these bacteria with a competitive advantage in the gut. Here, we have identified in the commensal species Lactobacillus casei a novel metabolic pathway for the utilization of the glycoamino acid fucosyl-α-1,6-N-GlcNAc-Asn, which is present in the core-fucosylated N-glycoproteins from mammalians. These results give insight into the molecular interactions between the host and commensal/probiotic bacteria and may help to devise new strategies to restore gut microbiota homeostasis in diseases associated with dysbiotic microbiota.

Synthetic and Biological Studies on New Urea and Triazole Containing Cystobactamid Derivatives.

Cystobactamids belong to the group of arene-based oligoamides that effectively inhibit bacterial type IIa topoisomerases. Cystobactamid 861-2 is the most active member of these antibiotics. Most amide bonds present in the cystobactamids link benzoic acids with anilines and it was found that some of these amide bonds undergo chemical and enzymatic hydrolysis, especially the one linking ring C with ring D. This work reports on the chemical synthesis and biological evaluation of thirteen new cystobactamids that still contain the methoxyaspartate hinge. However, we exchanged selected amide bonds either by the urea or the triazole groups and modified ring A in the latter case. While hydrolytic stability could be improved with these structural substitutes, the high antibacterial potency of cystobactamid 861-2 could only be preserved in selected cases. This includes derivatives, in which the urea group is positioned between rings A and B and where the triazole is found between rings C and D.

Intravenous injection of l-aspartic acid ß-hydroxamate attenuates choroidal neovascularization via anti-VEGF and anti-inflammation.

Choroidal neovascularization (CNV) is a hallmark of exudative age-related macular degeneration (exAMD) and a major cause of visual loss in AMD. Despite the widespread use of anti-VEGF therapy, serious adverse effects arise from repeated intravitreal injection of anti-VEGF antibodies, which warrant alternative strategy. We report herein that in a CNV murine model created by krypton red laser, intravenous injection of a serine racemase inhibitor, l-Aspartic acid ß-hydroxamate (L-ABH), significantly reduced CNV at the dose 6 mg/kg on the first day before and followed by 3 mg/kg on the third day after laser injury. The CNV volumes were analyzed with isolectin GS-IB4 staining on choroidal/RPE flat mounts on the seventh day after laser injury. Injection of L-ABH did not produce negative effects on retinal function and visual behavior. To dissect the mechanism in vitro, pretreatment with L-ABH in primary RPE cultures significantly reduced production of vascular endothelial growth factor (VEGF) and macrophage chemotactic protein 1 (MCP-1) by TNFα-primed RPEs. Consistent with these observations, L-ABH pretreatment significantly attenuated macrophage migration mediated by TNFα-primed RPE. Collectively, intravenous injection of L-ABH significantly reduced CNV volumes via reducing production of VEGF and MCP-1 by inflammation-primed RPEs.

Unique Binding Specificities of Proteins toward Isomeric Asparagine-Linked Glycans.

The glycan ligands recognized by Siglecs, influenza viruses, and galectins, as well as many plant lectins, are not well defined. To explore their binding to asparagine (Asn)-linked N-glycans, we synthesized a library of isomeric multiantennary N-glycans that vary in terminal non-reducing sialic acid, galactose, and N-acetylglucosamine residues, as well as core fucose. We identified specific recognition of N-glycans by several plant lectins, human galectins, influenza viruses, and Siglecs, and explored the influence of sialic acid linkages and branching of the N-glycans. These results show the unique recognition of complex-type N-glycans by a wide variety of glycan-binding proteins and their abilities to distinguish isomeric structures, which provides new insights into the biological roles of these proteins and the uses of lectins in biological applications to identify glycans.

Stapling of two PEGylated side chains increases the conformational stability of the WW domain via an entropic effect.

Hydrocarbon stapling and PEGylation are distinct strategies for enhancing the conformational stability and/or pharmacokinetic properties of peptide and protein drugs. Here we combine these approaches by incorporating asparagine-linked O-allyl PEG oligomers at two positions within the ß-sheet protein WW, followed by stapling of the PEGs via olefin metathesis. The impact of stapling two sites that are close in primary sequence is small relative to the impact of PEGylation alone and depends strongly on PEG length. In contrast, stapling of two PEGs that are far apart in primary sequence but close in tertiary structure provides substantially more stabilization, derived mostly from an entropic effect. Comparison of PEGylation + stapling vs. alkylation + stapling at the same positions in WW reveals that both approaches provide similar overall levels of conformational stability.

Adaptation of a Bacterial Multidrug Resistance System Revealed by the Structure and Function of AlbA.

To combat the rise of antimicrobial resistance, the discovery of new antibiotics is paramount. Albicidin and cystobactamid are related natural product antibiotics with potent activity against Gram-positive and, crucially, Gram-negative pathogens. AlbA has been reported to neutralize albicidin by binding it with nanomolar affinity. To understand this potential resistance mechanism, we determined structures of AlbA and its complex with albicidin. The structures revealed AlbA to be comprised of two domains, each unexpectedly resembling the multiantibiotic neutralizing protein TipA. Binding of the long albicidin molecule was shared pseudosymmetrically between the two domains. The structure also revealed an unexpected chemical modification of albicidin, which we demonstrate to be promoted by AlbA, and to reduce albicidin potency; we propose a mechanism for this reaction. Overall, our findings suggest that AlbA arose through internal duplication in an ancient TipA-like gene, leading to a new binding scaffold adapted to the sequestration of long-chain antibiotics.

Mn Inhibits GSH Synthesis via Downregulation of Neuronal EAAC1 and Astrocytic xCT to Cause Oxidative Damage in the Striatum of Mice.

Excessive manganese (Mn) can accumulate in the striatum of the brain following overexposure. Oxidative stress is a well-recognized mechanism in Mn-induced neurotoxicity. It has been proven that glutathione (GSH) depletion is a key factor in oxidative damage during Mn exposure. However, no study has focused on the dysfunction of GSH synthesis-induced oxidative stress in the brain during Mn exposure. The objective of the present study was to explore the mechanism of Mn disruption of GSH synthesis via EAAC1 and xCT in vitro and in vivo. Primary neurons and astrocytes were cultured and treated with different doses of Mn to observe the state of cells and levels of GSH and reactive oxygen species (ROS) and measure mRNA and protein expression of EAAC1 and xCT. Mice were randomly divided into seven groups, which received saline, 12.5, 25, and 50 mg/kg MnCl2, 500 mg/kg AAH (EAAC1 inhibitor) + 50 mg/kg MnCl2, 75 mg/kg SSZ (xCT inhibitor) + 50 mg/kg MnCl2, and 100 mg/kg NAC (GSH rescuer) + 50 mg/kg MnCl2 once daily for two weeks. Then, levels of EAAC1, xCT, ROS, GSH, malondialdehyde (MDA), protein sulfhydryl, carbonyl, 8-hydroxy-2-deoxyguanosine (8-OHdG), and morphological and ultrastructural features in the striatum of mice were measured. Mn reduced protein levels, mRNA expression, and immunofluorescence intensity of EAAC1 and xCT. Mn also decreased the level of GSH, sulfhydryl, and increased ROS, MDA, 8-OHdG, and carbonyl in a dose-dependent manner. Injury-related pathological and ultrastructure changes in the striatum of mice were significantly present. In conclusion, excessive exposure to Mn disrupts GSH synthesis through inhibition of EAAC1 and xCT to trigger oxidative damage in the striatum.

A critical analysis of L-asparaginase activity quantification methods-colorimetric methods versus high-performance liquid chromatography.

L-asparaginase or ASNase (L-asparagine aminohydrolase, E.C.3.5.1.1) is an enzyme clinically accepted as an antitumor agent to treat acute lymphoblastic leukemia (ALL) and lymphosarcoma through the depletion of L-asparagine (L-Asn) resulting in cytotoxicity to leukemic cells. ASNase is also important in the food industry, preventing acrylamide formation in processed foods. Several quantification techniques have been developed and used for the measurement of the ASNase activity, but standard pharmaceutical quality control methods were hardly reported, and in general, no official quality control guidelines were defined. To overcome this lack of information and to demonstrate the advantages and limitations, this work properly compares the traditional colorimetric methods (Nessler; L-aspartic acid ß-hydroxamate (AHA); and indooxine) and the high-performance liquid chromatography (HPLC) method. A comparison of the methods using pure ASNase shows that the colorimetric methods both overestimate (Nessler) and underestimate (AHA and indooxine) the ASNase activity when compared to the values obtained with HPLC, considered the most precise method as this method monitors both substrate consumption and product formation, allowing for overall mass-balance. Correlation and critical analysis of each method relative to the HPLC method were carried out, resulting in a demonstration that it is crucial to select a proper method for the quantification of ASNase activity, allowing bioequivalence studies and individualized monitoring of different ASNase preparations. Graphical abstract ᅟ.

Designing phenylalanine-based hybrid biological materials: controlling morphology via molecular composition.

Harnessing the self-assembly of peptide sequences has demonstrated great promise in the domain of creating high precision shape-tunable biomaterials. The unique properties of peptides allow for a building block approach to material design. In this study, self-assembly of mixed systems encompassing two peptide sequences with identical hydrophobic regions and distinct polar segments is investigated. The two peptide sequences are diphenylalanine and phenylalanine-asparagine-phenylalanine. The study examines the impact of molecular composition (namely, the total peptide concentration and the relative tripeptide concentration) on the morphology of the self-assembled hybrid biological material. We report a rich polymorphism in the assemblies of these peptides and explain the relationship between the peptide sequence, concentration and the morphology of the supramolecular assembly.

Structure of human immunoproteasome with a reversible and noncompetitive inhibitor that selectively inhibits activated lymphocytes.

Proteasome inhibitors benefit patients with multiple myeloma and B cell-dependent autoimmune disorders but exert toxicity from inhibition of proteasomes in other cells. Toxicity should be minimized by reversible inhibition of the immunoproteasome ß5i subunit while sparing the constitutive ß5c subunit. Here we report ß5i-selective inhibition by asparagine-ethylenediamine (AsnEDA)-based compounds and present the high-resolution cryo-EM structural analysis of the human immunoproteasome. Despite inhibiting noncompetitively, an AsnEDA inhibitor binds the active site. Hydrophobic interactions are accompanied by hydrogen bonding with ß5i and ß6 subunits. The inhibitors are far more cytotoxic for myeloma and lymphoma cell lines than for hepatocarcinoma or non-activated lymphocytes. They block human B-cell proliferation and promote apoptotic cell death selectively in antibody-secreting B cells, and to a lesser extent in activated human T cells. Reversible, ß5i-selective inhibitors may be useful for treatment of diseases involving activated or neoplastic B cells or activated T cells.

Nicrophorusamides A and B, Antibacterial Chlorinated Cyclic Peptides from a Gut Bacterium of the Carrion Beetle Nicrophorus concolor.

Nicrophorusamides A and B (1 and 2) were discovered from a rare actinomycete, Microbacterium sp., which was isolated from the gut of the carrion beetle Nicrophorus concolor. The structures of the nicrophorusamides were established as new chlorinated cyclic hexapeptides bearing uncommon amino acid units mainly based on 1D and 2D NMR spectroscopic analysis. The absolute configurations of the amino acid residues 5-chloro-l-tryptophan, d-threo-ß-hydroxyasparagine/d-asparagine, l-ornithine, l-allo-isoleucine, d-leucine, and d-valine were determined using Marfey's method and chemical derivatization with 2,3,4,6-tetra-O-acetyl-ß-d-glucopyranosyl isothiocyanate followed by LC/MS analysis. Nicrophorusamide A (1) showed antibacterial activity against several Gram-positive bacteria.

Total Syntheses of Cystobactamids and Structural Confirmation of Cystobactamid 919-2.

The cystobactamids are a family of antibacterial natural products with unprecedented chemical scaffolds that are active against both Gram-positive and Gram-negative pathogens. Herein, we describe the first total synthesis of cystobactamid 919-2 from three fragments. Our convergent synthesis enabled both the confirmation of the correct structure and the determination of the absolute configuration of cystobactamid 919-2.

Long chain fatty acids alter the interactive binding of ligands to the two principal drug binding sites of human serum albumin.

A wide variety of drugs bind to human serum albumin (HSA) at its two principal sites, namely site I and site II. A number of reports indicate that drug binding to these two binding sites are not completely independent, and that interactions between ligands of these two discrete sites can play a role. In this study, the effect of the binding of long-chain fatty acids on the interactive binding between dansyl-L-asparagine (DNSA; site I ligand) and ibuprofen (site II ligand) at pH6.5 was examined. Binding experiments showed that the binding of sodium oleate (Ole) to HSA induces conformational changes in the molecule, which, in turn, changes the individual binding of DNSA and ibuprofen, as well as the mode of interaction between these two ligands from a 'competitive-like' allosteric interaction in the case of the defatted HSA conformer to a 'nearly independent' binding in the case of non-defatted HSA conformer. Circular dichroism measurements indicated that ibuprofen and Ole are likely to modify the spatial orientation of DNSA at its binding site. Docking simulations suggest that the long-distance electric repulsion between DNSA and ibuprofen on defatted HSA contributes to a 'competitive-like' allosteric interaction, whereas extending the distance between ligands and/or increasing the flexibility or size of the DNSA binding site in fatted HSA evokes a change in the interaction mode to 'nearly independent' binding. The present findings provide further insights into the structural dynamics of HSA upon the binding of fatty acids, and its effects on drug binding and drug-drug interactions that occur on HSA.

Crystal structure of a mutant glycosylasparaginase shedding light on aspartylglycosaminuria-causing mechanism as well as on hydrolysis of non-chitobiose substrate.

Glycosylasparaginase (GA) is an amidase that cleaves Asn-linked glycoproteins in lysosomes. Deficiency of this enzyme causes accumulation of glycoasparagines in lysosomes of cells, resulting in a genetic condition called aspartylglycosaminuria (AGU). To better understand the mechanism of a disease-causing mutation with a single residue change from a glycine to an aspartic acid, we generated a model mutant enzyme at the corresponding position (named G172D mutant). Here we report a 1.8Å resolution crystal structure of mature G172D mutant and analyzed the reason behind its low hydrolase activity. Comparison of mature G172D and wildtype GA models reveals that the presence of Asp 172 near the catalytic site affects substrate catabolism in mature G172D, making it less efficient in substrate processing. Also recent studies suggest that GA is capable of processing substrates that lack a chitobiose (Glycan, N-acetylchiobios, NAcGlc) moiety, by its exo-hydrolase activity. The mechanism for this type of catalysis is not yet clear. l-Aspartic acid ß-hydroxamate (ß-AHA) is a non-chitobiose substrate that is known to interact with GA. To study the underlying mechanism of non-chitobiose substrate processing, we built a GA-ß-AHA complex structure by comparing to a previously published G172D mutant precursor in complex with a ß-AHA molecule. A hydrolysis mechanism of ß-AHA by GA is proposed based on this complex model.

Eficacia y seguridad de L-asparaginasa erwinia y L-asparaginasa E. Coli pegilada en el tratamiento de pacientes con leucemia linfoblástica aguda que presentam hipersensibilidad a L-asparaginasa E. coli nativa / Efficacy and safety of L-asparaginase erwinia and L-asparaginase E. coli pegylated in the treatment of patients with acute lymphoblastic leukemia who are hypersensitive to L-asparaginase E. coli native

INTRODUÇÃO: Antecedentes: El presente dictamen expone la evaluación de tecnología de la eficacia y seguridad del uso de L-asparaginasa Erwinia y L-asparaginasa E. coli pegilada para el tratamiento de pacientes con leucemia linfoblástica aguda que presentan hipersensibilidad a L-asparaginasa E. coli nativa. Aspectos Generales: La leucemia es el tipo de cáncer más común en niños, representando aproximadamente el 30% de todos los tipos de cáncer diagnosticados en niños; siendo la leucemia linfoblástica aguda (LLA) uno de los dos tipos de leucemias más comunes. Adicionalmente, alrededor del 60% de todos los casos de LLA ocurre en pacientes menores de 20 años. Así, LLA es un tipo de leucemia de alta importancia dentro de población joven. Tecnología Sanitaria de Interés: Las células neoplásicas en la leucemia linfoblástica aguda (LLA) no sintetizan las cantidades necesarias del aminoácido L-asparagina; por lo que requieren de funtes externas (i.e., L-asparagina extracelular). La L-asparaginasa, es una enzima que cataliza la conversión de L-asparagina más agua, en ácido aspártico y amoniaco, ocasionando que los niveles de L-asparagina extracelular disminuyan; y que por los tanto las células d ela LLA no cuenten con L-asparagina extracelular. Así, estas células neoplásicas se quedan sin fuentes de L-asparagina, y no pueden sintetizar proteínas de gran imporancia para su supervivencia, ocasionando su muerte. METODOLOGÍA: Estrategia de Búsqueda: Se realizó una búsqueda de la literatura a la eficacia y seguridad del uso de L-asparaginasa Erwinia y L-asparaginasa E. coli pegilada para el tratamiento de pacientes niños y adultos con leucemia linfoblástica aguda que presentan hipersensibilidad a L-asparaginasa E. coli nativa. Esta búsqueda se realizó utilizando los meta-buscadores: Translating Research into Practice (TRIPDATABASE) Y National Library of Medicine (Pubmed-Medline). RESULTADOS: Sinopsis de la Evidencia: Se realizó la búsqueda bibliográfica y de evidencia científica hasta marzo del 2017 para el sustento del uso de L-asparaginasa Erwinia en el tratamiento de leucemia linfoblástica aguda en pacientes niños y adultos que presentan hipersensibilidad a L-asparaginasa E. coli nativa. Se presente la evidencia disponible según el tipo de publicación priorizada en los criterios de inclusión (i.e., GP, ETS, RS y ECA fase III), siendo los ensayos de fase III o en su defecto ensayos controlados y aleatorizados la principal considerada. CONCLUSIONES: El presente dictamen evaluó la mejor evidencia disponible hasta marco 2017 en relación al uso de L-asparaginasa Erwinia y L-asparaginasa E. coli pegilada para el tratamiento de pacientes niños, adolescentes, y adultos con leucemia linfoblástica aguda, que presentan hipersensibilidad a L-asparaginasa E. coli nativa. El Instituto de Tecnologías Sanitarias-IETSI, aprueba el uso de L-asparaginasa Erwinia como parte del esquema quimioterápico utilizada para el tratamiento de pacientes niños, adolescentes, y adultos con leucemia linfoblástica aguda, que presentan hipersensibilidad grado 2 o más a L-asparaginasa E. coli nativa. La vigencia de este dictamen preliminar es de dos años a partir de la fecha de publicación. Asimismo, el Instituto de Tecnologías Sanitarias-IETSI, no aprueba el uso de L-asparaginasa E. coli pegilada en el tratamiento de pacientes niños, adolescentes, y adultos con leucemia linfoblástica aguda, que presentan hipersensiblidad grado 2 o más a L-asparaginasa E. coli nativa.

Use of peak sharpening effects to improve the separation of chiral compounds with molecularly imprinted porous polymer layer open-tubular capillaries.

This investigation demonstrates the application of a new peak sharpening technique to improve the separation of difficult-to-resolve racemic mixtures in capillary electro-chromatography. Molecularly imprinted porous layer open tubular (MIP-PLOT) capillaries, prepared by a layer-on-layer polymerization approach with Z-l-Asp-OH as the template, were selected to validate the approach. SEM revealed that the polymer film thickness can be varied by changes in both the polymer composition and the layer-on-layer regime. Capillaries made with methacrylic acid as the functional monomer could not separate the Z-Asp-OH racemate, due to weak interactions between the MIP-PLOT material and the target analytes. In contrast, MIP-PLOT capillaries prepared with 4-vinylpyridine as the functional monomer resulted in increased ionic interactions with the target analytes. Separation of the enantiomers could be enhanced when a peak zone sharpening effect was exploited through the use of specific BGE compositions and by taking advantage of eigenpeak phenomena. In this manner, the position of a sharpening zone and the peak shape of the sample analytes could be fine-tuned, so that when the sharpening zone and the target analyte co-migrated the separation of the Z-l-Asp-OH enantiomer from its d-enantiomer in a racemic mixture could be achieved under overloading conditions.