Construction of dual-chiral covalent organic frameworks for enantioselective separation.

Developing novel chiral stationary phases (CSPs) with versatility is of great importance in enantiomer separation. This study fabricated a dual-chiral covalent organic framework (PA-CA COF) via successive post-synthetic modifications. The chiral trans-1,2-cyclohexanediamine (CA) and (D)-penicillamine (PA) groups were periodically aligned within nanochannels of the COF, allowing selective recognition of enantiomers through intermolecular interactions. It can be a versatile high-performance liquid chromatography (HPLC) CSP for separating a wide range of enantiomers, including chiral pharmaceutical intermediates and chiral drugs. With separation performance comparable to commercial chiral columns and even greater versatility, the PA-CA COF@SiO2 column held promise for practical applications. Chiral separation results combined with molecular simulation indicated that the mixed mode of PA and CA resulted in the broad separation capability of PA-CA COF. The introduction of the dual-chiral COFs concept opens up a new avenue for chiral recognition and separation, holding great potential for practical enantiomer separation.

Copper nanoclusters stabilized by D-penicillamine for ultrasensitive and visual detection of oxytetracycline.

Copper nanoclusters (DPA@CuNCs) with red fluorescence were successfully synthesized by a one-step method based on D-penicillamine (DPA), which acted not only as a reducing agent but also as a stabilizer. The products were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, particle-size analysis, ultraviolet-visible spectrophotometry, and fluorescence spectrometry. When the excitation wavelength was 280 nm, DPA@CuNCs emitted bright red fluorescence at 640 nm with a fluorescence quantum yield of 5.8 %. Due to the inner filter effect, oxytetracycline (OTC) effectively quenched the fluorescence of DPA@CuNCs, and then DPA@CuNCs were applied to the trace detection of OTC. The method showed a good linear range for OTC from 5 to 60 µmol/L, with a detection limit of 0.026 µmol/L and a correlation coefficient R2 of 0.9983. Moreover, a paper-based sensor for the visual detection of OTC has been developed, which can conveniently and rapidly distinguish the concentration ranges of OTC through the color changes of the test papers.

Glutathione, Cysteine, and D-Penicillamine Role in Exchange of Silver Metal from the Albumin Metal Complex.

The purpose of this study is to investigate the exchange reaction taking place among the bovine serum albumin (BSA), 5,5'-dithiobis-(2-nitrobenzoic acid (ESSE), reduced glutathione, N-acetylcysteine, D-penicillamine (thiolates), and silver metal (AgI). For this purpose, stock solutions of BSA and Ellman's reagent were prepared by dissolving 264 mg of BSA in 5 ml of reaction buffer (0.1 M KH2PO4 at pH 7.8) and 23.8 mg of ESSE in 1.0 ml of reaction buffer which were mixed together. Mixture of BSA-AgI was prepared in a separate procedure by dissolving 0.17 mg of silver nitrate in 1 ml of reaction buffer and then dissolving BSA (200 mg) in the same solution of silver nitrate. Blocking of Cys-34 of BSA with AgI was confirmed by treating different dilutions of BSA-AgI (500 µM) solutions with the solutions of ESSE (85 µM) and ES- (85 µM) and recording the spectra (300-450) with a UV-visible spectrophotometer. The chromatographed AgI-modified BSA ((BSA-S)AgI)) samples (typically 500 µM) were subsequently mixed with thiolates (reduced glutathione, N-acetylcysteine, and D-penicillamine). AgI and modified BSA (typically 500 µM each) were treated with these low molecular weight thiolates and allowed to react overnight followed by chromatographic separation (Sephadex G25). The redox reactions of AgI-modified BSA with various low molecular weight thiols revealed a mechanically important phenomenon. In the case of reduced glutathione and N-acetylcysteine, we observed the rapid release of a commensurate amount of Ellman's anion, indicating that an exchange has taken place and low molecular weight thiols (RSH) substituted AgI species at the Cys-34 of BSA eventually forming disulfide (BSA-SSR) at Cys-34. It can be anticipated from the phase of study involving bovine serum albumin that low molecular weight thiolates (reduced glutathione and N-acetylcysteine) take off AgI which are attached to proteins elsewhere in the physiological system, making these toxic metals free for toxic action.

Inspecting the structural characteristics of chiral drug penicillamine under different pH conditions using Raman optical activity spectroscopy and DFT calculations.

The investigation of the structural characteristics of chiral drugs in physiological environments is a challenging research topic, which may lead to a better understanding of how the drugs work. Raman optical activity (ROA) spectroscopy in combination with density functional theory (DFT) calculations was exploited to inspect the structural changes in penicillamine under different acid-base states in aqueous solutions. The B3LYP/aug-cc-PVDZ method was employed and the implicit solvation model density (SMD) was considered for describing the solvation effect in H2O. The conformations of penicillamine varied with pH, but penicillamine was liable to stabilize in the form of the PC conformation (the sulfur atom is in a trans orientation with respect to carboxylate) in most cases for both D- and L-isomers. The relationship between the conformations of penicillamine and the ROA peaks, as well as peak assignments, were comprehensively studied and elucidated. In the fingerprint region, two ROA couplets and one ROA triplet with different patterns were recognized. The intensity, sign and frequency of the corresponding peaks also changed with varying pH. Deuteration was carried out to identify the vibrational modes, and the ROA peaks of the deuterated amino group in particular are sensitive to change in the ambient environment. The results are expected not only to serve as a reference for the interpretation of the ROA spectra of penicillamine and other chiral drugs with analogous structures but also to evaluate the structural changes of chiral molecules in physiological environments, which will form the basis of further exploration of the effects of structural characteristics on the pharmacological and toxicological properties of chiral drugs.

Sensitive recognition of ractopamine using GQDs-DPA as organic fluorescent probe.

A novel spectrofluorimetric sensing platform was designed for Ractopamine measurement in aqueous and plasma samples. d-penicillamine functionalized graphene quantum dots (DPA-GQDs) was utilized as a fluorescence probe, which was synthesized through the pyrolysis of citric acid in the presence of DPA. This one-pot down-top strategy causes to high-yield controllable synthesis method. The reaction time and probe concentration were optimized. Then, the fluorescence intensity of aqueous samples containing different Ractopamine concentrations and 500 ppm DPA-GQDs were measured at 25°C with an excitation wavelength of 274 nm. The sensing platform was also applied to detect Ractopamine in untreated plasma samples. The fluorescence spectroscopy technique responses indicated a linear relationship between the peak fluorescence intensity and ractopamine concentration in the range of 0.25-15 ppm with low limit of quantification of 0.25 ppm was for aqueous and plasma samples, respectively.

pH-modulated aggregation-induced emission of Au/Cu nanoclusters and its application to the determination of urea and dissolved ammonia.

A fluorescence platform is designed based on aggregation-induced emission of Au/Cu nanoclusters (Au/Cu NCs) driven by pH value. When pH increases from 6.0 to 7.0, Au/Cu NCs change from aggregation to dispersion, accompanied by the oxidation of Cu cores. Under the catalysis of urease, urea is hydrolysed to release ammonia, which further undergoes a hydrolysis reaction to produce OH-, causing the pH to increase. The fluorescence of Au/Cu NCs quenches linearly at 590 nm with the excitation wavelength at 320 nm when the concentration of urea varies from 5.0 to 100 µM. The limit of detection (LOD) and limit of quantification (LOQ) of urea are 2.23 and 7.45 µM, respectively. Combined with headspace single-drop microextraction technology, Au/Cu NCs are employed to monitor dissolved ammonia with low-cost and simple operation. The linear range of dissolved ammonia is from 20 to 300 µM. The LOD and LOQ of dissolved ammonia are 7.04 and 23.4 µM, respectively. The relative standard deviation (RSD) values of the intra-day and inter-day precision of urea are 2.4-3.0% and 3.0-3.7%, respectively, and those of dissolved ammonia are in the range 3.4-5.1% (intra-day precision) and 4.2-5.8% (inter-day precision). No interferences have been indentified in the determination of urea and dissolved ammonia. Finally, the proposed method has been applied to determine urea in human urine samples and dissolved ammonia in water samples with satisfactory results.Graphical abstract The pH increase produces the dispersion and decomposition of Au/Cu NCs, leading to the fluorescence quenching. Both urea and dissolved ammonia are detected successfully because they cause the pH change to alkaline.

D-penicillamine modified copper nanoparticles for fluorometric determination of histamine based on aggregation-induced emission.

A fluorometric method for the determination of histamine has been developed based on aggregation-induced emission (AIE) effect of D-penicillamine capped copper nanoparticles (DPA-CuNPs). The fluorescent DPA-CuNPs were synthesized by a one-pot method using D-penicillamine as both reducing agent and stabilizing ligand. The size, morphology and physical chemical properties of DPA-CuNPs were examined by transmission electron microscopy (TEM), fluorescence spectroscopy, fourier transform infrared spectroscopy (FTIR) and absorption spectroscopy. The DPA-CuNPs exhibit AIE effect and show intense red fluorescence (650 nm). In the presence of histamine, DPA-CuNPs are dispersed into small homogeneous particles, causing fluorescence quenching. Based on this reaction, a histamine sensor is constructed. The fluorescence of the CuNPs solution has a good linear relationship with histamine concentration in the range 0.05 µM to 5 µM and the determination limit (3σ/slope) is 30 nM. The estimated method was successfully applied to the determination of histamine in fish, pork and red wine. Graphical abstract Schematic representation of copper nanoparticles for histamine analysis. In the presence of histamine, the strong red fluorescence of copper nanoparticles is obvious decreased through interaction of copper nanoparticles and histamine.

Investigation of the synergistic effect with chiral D-penicillamine functionalized gold nanoparticle as an additive for enantiomeric separation in capillary electrophoresis.

The authors describe a synergistic system for nanoparticle based chiral separation. It is based on the use of a conventional chiral selector hydroxyproyl-ß-cyclodextrin and a kind of gold nanoparticle functionalized with D-penicillamine as an additive. This nanomaterial displays a synergistic effect on the efficiency of the enantioseparation of the chiral drugs amlodipine, tropicamide, and ofloxacin. A comparative study on the enantioseparation capability of three separation systems, viz. (a) single hydroxyproyl-ß-cyclodextrin system, (b) achiral citrate capped gold nanoparticle/ hydroxyproyl-ß-cyclodextrin system, and (c) chiral D-penicillamine functionalized gold nanoparticle/ hydroxyproyl-ß-cyclodextrin system was performed. The results show that the D-penicillamine functionalized gold nanoparticle/hydroxyproyl-ß-cyclodextrin synergistic system has remarkable superiority. The effects of concentrations of D-penicillamine functionalized gold nanoparticle and hydroxyproyl-ß-cyclodextrin, of buffer pH value and concentration, and of applied voltage on the performance of enantioseparation were investigated.

Noncoded Amino Acids in de Novo Metalloprotein Design: Controlling Coordination Number and Catalysis.

The relationship between structure and function has long been one of the major points of investigation in Biophysics. Understanding how much, or how little, of a protein's often complicated structure is necessary for its function can lead to directed therapeutic strategies and would allow one to design proteins for specific desired functions. Studying protein function by de novo design builds the functionality from the ground up in a completely unrelated and noncoded protein scaffold. Our lab has used this strategy to study heavy and transition metal binding within the TRI family of three stranded coiled coil (3SCC) constructs to understand coordination geometry and metalloenzyme catalytic control within a protein environment. These peptides contain hydrophobic layers within the interior of the 3SCC, which one can mutate to metal binding residues to create a minimal metal binding site, while solid phase synthesis allows our lab to easily incorporate a number of noncoded amino acids including d enantiomers of binding or secondary coordination sphere amino acids, penicillamine, or methylated versions of histidine. Our studies of Cd(II) binding to Cys3 environments have determined, largely through the use of 113Cd NMR and 111mCd PAC, that the coordination environment around a heavy metal can be controlled by incorporating noncoded amino acids in either the primary or secondary coordination spheres. We found mutating the metal binding amino acids to l-Pen can enforce trigonal Cd(II)S3 geometry exclusively compared to the mixed coordination determined for l-Cys coordination. The same result can be achieved with secondary sphere mutations as well by incorporating d-Leu above a Cys3. We hypothesize this latter effect is due to the increased steric packing above the metal binding site that occurs when the l-Leu oriented toward the N-terminus of the scaffold is mutated to d-Leu and oriented toward the C-terminus. Mutating the layer below Cys3 to d-Leu instead formed a mixed 4- and 5-coordinate Cd(II)S3(H2O) and Cd(II)S3(H2O)2 construct as steric bulk was decreased below the metal binding site. We have also applied noncoded amino acids to metalloenzyme systems by incorporating His residues that are methylated at the δ- or ε-nitrogen to enforce Cu(I) ligation to the opposite open nitrogen of His and found a 2 orders of magnitude increased catalytic efficiency for nitrite reductase activity with ε-nitrogen coordination compared to δ-nitrogen. These results exemplify the ability to tune coordination environment and catalytic efficiency within a de novo scaffold as well as the utility of noncoded amino acids to increase the chemist's toolbox. By furthering our understanding of metalloprotein design one could envision, through our use of amino acids not normally available to nature, that protein design laboratories will soon be capable of outperforming the native systems previously used as their benchmark of successful design. The ability to design proteins at this level would have far reaching and exciting benefits within various fields including medical and industrial applications.

Preparation of epoxy-functionalized hierarchically porous hybrid monoliths via free radical polymerization and application in HILIC enrichment of glycopeptides.

Owing to their multiscale pore size regimes and unique properties, the materials with hierarchically porous structures have become an important family of functional materials in recent years. They have been applied from energy conversion and storage, catalysis, separation to drug delivery, etc. The synthesis of them is difficult by the need to employ multiple templates and take complicated steps. Herein, we successfully prepared epoxy-functionalized hierarchically porous hybrid monoliths (HPHMs) with micro/meso/macro-structures in an easy way. Firstly, a bulk monolithic material was formed via free radical polymerization between polyhedral oligomeric vinylsilsesquioxanes (vinylPOSS) and allyl glycidyl ether (AGE) in the presence of polycaprolactone (PCL). Then PCL was degraded with hydrochloric acid solution, and the epoxy-functionalized HPHM was obtained. This approach was very simple and suitable for large-scale preparation. Hybrid monoliths with different specific surface area (from 5.4 to 636.7 m2/g) were prepared by adjusting the mole ratio of vinylPOSS to AGE and the content of PCL. The results of several characterization methods, including nitrogen adsorption/desorption measurements, scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), showed that these materials contained not only micropores and mesopores but also macropores. The materials were further modified with penicillamine to be used as hydrophilic interaction chromatography (HILIC) adsorbents for enriching N-glycopeptides in IgG and serum protein tryptic digests. Up to 23 N-glycopeptides were identified from IgG digest, and 385 N-glycopeptides and 283 N-glycosylation sites were identified from human serum digest.

Size-dependent electrophoretic migration and separation of water-soluble gold nanoclusters by capillary electrophoresis.

Recently, water-soluble gold nanoclusters (AuNCs) have attracted more and more attention due to their unique properties. In this study, penicillamine-protected gold nanoclusters (Pen-AuNCs) were synthesized and initially fractionated by sequential size-selective precipitation (SSSP). The crude Pen-AuNCs and SSSP fractions were separated by capillary zone electrophoresis (CZE) with a diode array detector. The effects of key parameters, including the concentration of phosphate buffer, pH value and the ethanol content were systematically investigated. The separation of water-soluble poly-disperse AuNCs were well achieved at 30 mM phosphate buffer with 7.5% EtOH, pH 12.0, and applied voltage of 15 kV. The linear correlation between AuNCs diameter and mobility was observed. This finding provides an important reference for CE separation and product purification of water-soluble AuNCs or other nanomaterials.

Highly selective circular dichroism sensor based on d-penicillamine/cysteamine­cadmium sulfide quantum dots for copper (II) ion detection.

A highly selective circular dichroism sensor based on cysteamine-capped cadmium sulfide quantum dots (Cys-CdS QDs) was successfully developed for the determination of Cu2+. Basically, the Cys-CdS QDs are not active in circular dichroism spectroscopy. However, the circular dichroism probe (DPA@Cys-CdS QDs) can be simply generated in situ by mixing achiral Cys-CdS QDs with D-penicillamine. The detection principle was based on measuring the circular dichroism signal change upon the addition of Cu2+. The strong CD signal of the DPA@Cys-CdS QDs dramatically decreased in the presence of Cu2+, while other cations did not result in any spectral changes. In addition, the degree of the CD signal decrease was linearly proportional to the concentration of Cu2+ in the range of 0.50-2.25 µM (r2 = 0.9919) with a detection limit of 0.34 µM. Furthermore, the proposed sensor was applied to detect Cu2+ in drinking water samples with %recovery values of 102-114% and %RSD less than 6%.

Diagnosis of penicillin allergy: a MOFs-based composite hydrogel for detecting ß-lactamase in serum.

An as-synthesized MOFs-based hydrogel exhibits high sensitivity for ß-lactamase through an "ON-OFF-OFF-ON" luminescence trigger. It allows achieving an unprecedented strategy for the judgement of penicillin allergy via luminescence detection of ß-lactamase in serum.

Sensitive and Selective Detection of Antibiotic D-Penicillamine Based on a Dual-Mode Probe of Fluorescent Carbon Dots and Gold Nanoparticles.

This paper reported a dual-mode probe for D-penicillamine on the basis of pH-mediated gold nanoparticles aggregation and fluorescence resonance energy transfer (FRET) from carbon dots. D-penicillamine is a zwitterionic compound and has different forms depending on specific pH ranges. The thiol group of D-penicillamine has high affinity towards the surface of gold nanoparticles and can replace other surface ligands. When pH values were close to its isoelectrical point (pH(I)), the D-penicillamine capped gold nanoparticles aggregated through hydrogen bonding or electrostatic interactions, resulting in the releasing of carbon dots from gold nanoparticles. The dual-mode probe consisted of fluorescent carbon dots and gold nanoparticles, and the fluorescence of carbon dots was quenched by the attached gold nanoparticles due to the FRET. Then, the fluorescence can be recovered in presence of D-penicillamine due to the gold nanoparticles aggregation in specific pH range. Under the optimum conditions, the probe has linear response for D-penicillamine in the 0.25-1.5 µM concentration range with a detection limit of 0.085 µM. This method provides a potential application in sensitive detection of D-penicillamine.

Nanoparticle-based Chemiluminescence for Chiral Discrimination of Thiol-Containing Amino Acids.

The ability to recognize the molecular chirality of enantiomers is extremely important owing to their critical role in drug development and biochemistry. Convenient discrimination of enantiomers has remained a challenge due to lack of unsophisticated methods. In this work, we have reported a simple strategy for chiral recognition of thiol-containing amino acids including penicillamine (PA), and cysteine (Cys). We have successfully designed a nanoparticle-based chemiluminescence (CL) system based on the reaction between cadmium telluride quantum dots (CdTe QDs) and the enantiomers. The different interactions of CdTe QDs with PA enantiomers or Cys enantiomers led to different CL intensities, resulting in the chiral recognition of these enantiomers. The developed method showed the ability for determination of enantiomeric excess of PA and Cys. It has also obtained an enantioselective concentration range from 1.15 to 9.2 mM for PA. To demonstrate the potential application of this method, the designed platform was applied for the quantification of PA in urine and tablet samples. For the first time, we presented a novel practical application of nanoparticle-based CL system for chiral discrimination.

Pentaethylenehexamine and d-penicillamine co-functionalized graphene quantum dots for fluorescent detection of mercury(II) and glutathione and bioimaging.

Pentaethylenehexamine and d-penicillamine co-functionalized graphene quantum dots (PEHA-GQD-DPA) was made via one two-step thermal pyrolysis. The resulting PEHA-GQD-DPA is composed of the graphene sheets with an average size of 3.16 nm and the rich of functional groups. It gives an ultra strong fluorescence emission with the fluorescent quantum yield of 90.91% and sensitive and selective optical response towards Hg2+. The fluorescence intensity linearly decreases with the increase of Hg2+ in the range of 1.0 × 10-10-2 × 10-4 M with the detection limit of 4.6 × 10-11 M (S/N = 3). No species tested interfere with detection of Hg2+. The fluorescence quenched by Hg2+ can be well recovered by glutathione. The fluorescence intensity linearly increases with the increase of glutathione in the range of 5 × 10-8-2.5 × 10-6 M with the detection limit of 1.7 × 10-8 M (S/N = 3). The PEHA-GQD-DPA as a fluorescence probe has been successfully applied in determination of Hg2+ in natural water and glutathione in human serum and SW480 cell imaging.

A phage display-based strategy for the de novo creation of disulfide-constrained and isomer-free bicyclic peptide affinity reagents.

Bicyclic peptides have been attractive scaffolds for developing high affinity reagents for biomacromolecules. Here we report a general phage-screening strategy for the development of bicyclic peptide ligands constrained with isomerically-forbidden disulfide bridges without elaborate chemical modifications and recourses to genetic code reprogramming.

Coordination-Mediated Synthesis of Purification-Free Bivalent 99mTc-Labeled Probes for in Vivo Imaging of Saturable System.

In the synthesis of technetium-99m (99mTc) labeled target-specific ligands, the presence of a large excess of unlabeled ligands over 99mTc in the injectate hinders target accumulation of 99mTc-labeled ligands by competing for target molecules. To circumvent the problem, we recently developed a concept of the metal coordination-mediated multivalency, and proved the concept with a 99mTc-labeled trivalent compound [99mTc(CO)3(CN-RGD)3]+. In this study, D-penicillamine (Pen) was selected as a chelating molecule and a cyclic RGDfK peptide was conjugated to Pen via a hexanoic linkage (Pen-Ahx-c(RGDfK)). 99mTc complexation reaction, and the stability, integrin αvß3 binding affinity, and biodistribution of the 99mTc-labeled probe were investigated to evaluate the applicability of the concept to bivalent probes. 99mTc-[Pen-Ahx-c(RGDfK)]2 was obtained over 95% radiochemical yields under low Pen-Ahx-c(RGDfK) concentration (50 µM). 99mTc-[Pen-Ahx-c(RGDfK)]2 showed approximately 10-times higher integrin αvß3 binding affinity than the monovalent compounds, Pen-Ahx-c(RGDfK) and c(RGDyV). In biodistribution studies, the tumor accumulation of 99mTc-[Pen-Ahx-c(RGDfK)]2 was decreased to 77% and 43% of HPLC-purified (Pen-Ahx-c(RGDfK)-free) 99mTc-[Pen-Ahx-c(RGDfK)]2 by the presence of 5 nmol of unlabeled Pen-Ahx-c(RGDfK) and Re-[Pen-Ahx-c(RGDfK)]2, respectively. 99mTc-[Pen-Ahx-c(RGDfK)]2 provided tumor image without removing unlabeled ligand, while a 99mTc-labeled monovalent probe prepared from a monovalent ligand could not. These findings indicate the availability of the design concept to prepare 99mTc-labeled bivalent probes with a variety of 99mTc core and other metallic radionuclides of clinical relevance.

Report: Palladium glutathione, N-acetylcysteine, D-penicillamine conjugation chemistry.

The metalloelement Palladium has a number of potential Pharmaco-clinical advantages. Palladium compounds have antiviral, antibacterial, neuroprotective and antitumor properties. However studies have also indicated some mild to serious toxic effects of Palladium metalloelements. Biothiols are important antioxidants that provide protection against metals toxicity. The interaction of metalloelements with biothiols can provide valuable information about the level of toxicity of the metalloelements and about the protective role of biothiols thereof. In this piece of work the effect of salt and complexes of Palladium on the status of different thiols (GSH, NAC, and D-Pen) in aqueous medium, were examined, The thiol quantification was carried out using Elman's method through UV-visible spectrophotometry and 1H- NMR. Results of the study performed in aqueous medium showed that level of different thiols depleted after the addition of the inorganic salts and organic complexes of Palladium. The mechanism of interaction of Palladium with thiols was examined using H-NMR. The results indicate that the depletion in the level of thiols may be due to 1:1 or 1:2 conjugation of Palladium with thiols. These conjugation reactions further suggest that the Palladium have xenobiotic nature causing oxidative stress and thiols play their role in detoxification and biotransformation of these metalloelements.

Direct HPLC separation of carnosine enantiomers with two chiral stationary phases based on penicillamine and teicoplanin derivatives.

Carnosine is present in high concentrations in specific human tissues such as the skeletal muscle, and among its biological functions, the remarkable scavenging activity toward reactive carbonyl species is noteworthy. Although the two enantiomers show almost identical scavenging reactivity toward reactive carbonyl species, only d-carnosine is poorly adsorbed at the gastrointestinal level and is stable in human plasma. Direct methods for the enantioselective analysis of carnosine are still missing even though they could find more effective applications in the analysis of complex matrices. In the present study, the use of two different chiral stationary phases is presented. A chiral ligand-exchange chromatography stationary phase based on N,S-dioctyl-d-penicillamine resulted in the direct enantioseparation of carnosine. Indeed, running the analysis at 25°C and 1.0 mL/min with a 1.5 mM copper(II) sulfate concentration allowed us to obtain separation and resolution factors of 3.37 and 12.34, respectively. However, the use of a copper(II)-containing eluent renders it hardly compatible with mass spectrometry detectors. With the teicoplanin-based stationary phase, a mass spectrometry compatible method was successfully developed. Indeed, a water/methanol 60:40 v/v pH 3.1 eluent flowed at 1.0 mL/min and with a 25°C column temperature produced separation and resolution factors of 2.60 and 4.16, respectively.