Carboxyl Reduction Research Articles

A novel Stauntonia leucantha fruits arabinogalactan: isolation and structural characterization

Polysaccharides were the key ingredients of many herbal medicines, and were responsible for multiple pharmacological activities. In this study, a novel polysaccharide fraction, named SLP-2, was isolated from Stauntonia leucantha fruits, and purified by DEAE-52 and Sephadex G-100 column chromatography. Furthermore, SLP-2 was identified by congo red, methylation, partial acid hydrolysis and NMR. The results indicated that the backbone of SLP-2 was composed of →4)-β-D-Galp-(1 → 4)-β-D-Galp-(1→ substituted at C-6 with 1,5-linked arabinan. SLP-2 had good anti-oxidation ability in vitro. Surprisingly, we found that reduction of carboxyl groups and methylation of hydroxyl groups enhanced the ability to scavenge 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radicals and inhibit lipid peroxidation, and weakened the activity to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and reduce ferric iron.

Biotransformation of ursolic acid by Circinella muscae and their anti-neuroinflammatory activities of metabolites

In this study, the biotransformation of ursolic acid by Circinella muscae CGMCC 3.2695 was investigated. Scaled-up biotransformation reactions yielded ten metabolites. Their structures were established based on extensive NMR and HR-ESI-MS data analyses, and four of them are new compounds. C. muscae could selectively catalyze hydroxylation, lactonisation, carbonylation and carboxyl reduction reactions. Furthermore, all the identified metabolites were evaluated for their anti-neuroinflammatory activities in LPS-induced BV-2 cells. Most metabolites displayed pronounced inhibitory effect on nitric oxide (NO) production. The results suggested that biotransformed derivatives of ursolic acid might be served as potential neuroinflammatory inhibitors.

A TEMPO-catalyzed oxidation–reduction method to probe surface and anhydrous crystalline-core domains of cellulose microfibril bundles

A modified TEMPO-catalyzed oxidation of the solvent-exposed glucosyl units of cellulose to uronic acids, followed by carboxyl reduction with NaBD4 to 6-deutero- and 6,6-dideuteroglucosyl units, provided a robust method for determining relative proportions of disordered amorphous, ordered surface chains, and anhydrous core-crystalline residues of cellulose microfibrils inaccessible to TEMPO. Both glucosyl residues of cellobiose units, digested from amorphous chains of cellulose with a combination of cellulase and cellobiohydrolase, were deuterated, whereas those from anhydrous chains were undeuterated. By contrast, solvent-exposed and anhydrous residues alternate in surface chains, so only one of the two residues of cellobiosyl units was labeled. Although current estimates indicate that each cellulose microfibril comprises only 18 to 24 (1 → 4)-β-d-glucan chains, we show here that microfibrils of walls of Arabidopsis leaves and maize coleoptiles, and those of secondary wall cellulose of cotton fibers and poplar wood, bundle into much larger macrofibrils, with 67 to 86% of the glucan chains in the anhydrous domain. These results indicate extensive bundling of microfibrils into macrofibrils occurs during both primary and secondary wall formation. We discuss how, beyond lignin, the degree of bundling into macrofibrils contributes an additional recalcitrance factor to lignocellulosic biomass for enzymatic or chemical catalytic conversion to biofuel substrates.

Chemical and structural properties of reduced graphene oxide\u2014dependence on the reducing agent

Graphene oxide (GO) prepared from graphite powder using a modified Hummers method and reduced graphene oxide (rGO) obtained from GO using different reductants, i.e., sodium borohydride, hydrazine, formaldehyde, sodium hydroxide and L-ascorbic acid, were investigated using transmission electron microscopy, X-ray diffraction, Raman, infrared and electron spectroscopic methods. The GO and rGOs’ stacking nanostructure (flake) size (height x diameter), interlayer distance, average number of layers, distance between defects, elementary composition, content of oxygen groups, C sp3 and vacancy defects were determined. Different reductants applied to GO led to modification of carbon to oxygen ratio, carbon lattice (vacancy) and C sp3 defects with various in-depth distribution of C sp3 due to oxygen group reduction proceeding as competing processes at different rates between interstitial layers and in planes. The reduction using sodium borohydride and hydrazine in contrary to other reductants results in a larger content of vacancy defects than in GO. The thinnest flakes rGO obtained using sodium borohydride reductant exhibits the largest content of vacancy, C sp3 defects and hydroxyl group accompanied by the smallest content of epoxy, carboxyl and carbonyl groups due to a mechanism of carbonyl and carboxyl group reduction to hydroxyl groups. This rGO similar diameter to GO seems to result from a predominant reduction rate between the interstitial layers. The thicker flakes of a smaller diameter than in GO are obtained in rGOs prepared using remaining reductants and result from a higher rate of reduction of in plane defects.

One‐Pot Three‐Step Consecutive Transformation of L‐α‐Amino Acids to (R)‐ and (S)‐Vicinal 1,2‐Diols via Combined Chemical and Biocatalytic Process

AbstractOptically pure vicinal 1,2‐diols are versatile chiral building blocks in the fine chemical and pharmaceutical industries. L‐α‐amino acid is a good feedstock source for high value‐added product production since it is inexpensive and renewable. However, conversion of L‐α‐amino acids to enantioenriched vicinal 1,2‐diols remains a significant challenge. In this study, combining a simple chemical process and a three‐enzyme cascade biocatalysis system, we have successfully implemented a one‐pot sequential process for the transformation of L‐α‐amino acids into enantiopure vicinal 1,2‐diols in aqueous medium. Firstly, the NaBH4‐H2SO4 system converted L‐α‐amino acids to (S)‐amino alcohols via amino acid carboxyl reduction. Secondly, the three‐enzyme (transaminase, carbonyl reductase and glucose dehydrogenase) cascade biocatalysis system converted amino alcohols to enantiopure vicinal 1,2‐diols via amino alcohol deamination, α‐hydroxy ketone asymmetric reduction and cofactor regeneration. Taking advantage of the two different reaction systems, chiral vicinal 1,2‐diols could be obtained from L‐α‐amino acids with high yields (69–90 %) and excellent ee values (91–>99 % ee).

Biochemical and biophysical characterization of water-soluble pectin from Opuntia ficus-indica and its potential cytotoxic activity

This work aims to fill the gap in the present knowledge about the structure of pectin from Opuntia ficus-indica. The water-soluble pectin (WSP) fraction, extracted with the Microwave Assisted Extraction (MAE), was further deproteinated (dWSP) and analyzed through several biophysical and biochemical techniques. HPSEC, light scattering and FTIR data showed that dWSP is low methylated high molecular weight pectin. The biochemical structure of dWSP, after methanolysis, silylation, carboxyl reduction showed that dWSP belongs to rhamnogalacturonan I class. Then, dWSP was heat-modified (HM) to obtain small-molecular weight deproteinated fraction (HM-dWSP). Both species, dWSP and HM-dWSP, were tested in LAN5 and NIH 3T3 model cells to study their biological effect. Results indicated that both dWSP and HM-dWSP exerted cytotoxic activity affecting selectively LAN5 cancer cells, without any effect on NIH 3T3 normal cells.

Structural Features and Anti-Complement Activity of an Acidic Polysaccharide from Forsythia suspensa

Background: The complement system is an important host defence mechanism against the invasion of foreign materials. However, excessive or uncontrolled activation of the complement system might lead to severe complement-mediated disorders which are harmful to human bodies. There are still no desirable therapeutic compounds available on the market for complement inhibition. In recent years, researches have been focused on natural polysaccharides to modulate of the immune system because of their immunomodulatory activities and safety. In this study, Fs-8-ba2, a homogeneous acidic polysaccharide (MW ca. 7.2 kDa) was isolated from Forsythia suspensa and its anti-complementary effect was investigated. Method: The major primary structural features of Fs-8-ba2 were elucidated using HPGPC, IR, absolute configuration, component analysis and methylation analysis, periodate oxidation, carboxyl reduction partial acid hydrolysis, and NMR spectroscopy, etc. To identify the anti-complementary activity of Fs-8-ba2, the hemolytic assays through the classical pathway (CP) and the alternative pathway (AP) of complement system in vitro were taken. Results: The backbone of Fs-8-ba2 was composed of 7 homogalacturonan (HG) and 2 rhamnogalacturonan (RG-I) moieties with the side chains attached at O-4 of 1,2,4-linked α-L-Rha in the RG-I moieties. The anti-complement assay showed that the native acidic polysaccharide (Fs-8-ba2) possessed stronger inhibitory effect on the complement activation than the carboxyl-reduced polysaccharide (Fs-8-ba2re) through the classical (IC50: 0.311 ± 0.020 mg/mL vs. 3.292 ± 0.032 mg/mL) and alternative pathways (IC50: 0.218 ± 0.015 mg/mL vs. no activity). It indicated that the anti-complement effect of pectic polysaccharide was related to GalA content (carboxyl group). Preliminary mechanism studies by using complement-depleted sera indicated that Fs-8-ba2 selectively interacted with C1q, C1r, C1s, C2, C3 and C9, but not C4 and C5. Conclusion: These results suggested that Fs-8-ba2, an acidic polysaccharide, could be of potential benefits in the treatment of the complement-mediated diseases.

Structure and biological activity of a fucosylated chondroitin sulfate from the sea cucumber Cucumaria japonica.

A fucosylated chondroitin sulfate (FCS) was isolated from the body wall of Pacific sea cucumber Cucumaria japonicaby extraction in the presence of papain followed by Cetavlon precipitation and anion-exchange chromatography. FCS was shown to contain D-GalNAc, D-GlcA, L-Fuc and sulfate in molar proportions of about 1:1:1:4.5. Structure of FCS was elucidated using NMR spectroscopy and methylation analysis of the native polysaccharide and products of its desulfation and carboxyl reduction. The polysaccharide was shown to contain a typical chondroitin core → 3)-β-D-GalNAc-(1 → 4)-β-D-GlcA-(1 →. Sulfate groups in this core occupy O-4 and the majority of O-6 of GalNAc. Fucosyl branches are represented by 3,4- and 2,4-disulfated units in a ratio of 4:1 and are linked to O-3 of GlcA. In addition, ∼ 33% of GlcA are 3-O-sulfated, and hence, the presence of short fucooligosaccharide chains side by side with monofucosyl branches cannot be excluded. FCS was shown to inhibit platelets aggregation in vitro mediated by collagen and ristocetin, but not adenosine diphosphate, and demonstrated significant anticoagulant activity, which is connected with its ability to enhance inhibition of thrombin and factor Xa by antithrombin III, as well as to influence von Willebrand factor activity. The latest property significantly distinguished FCS from low-molecular-weight heparin.

Self-sufficient redox biotransformation of lignin-related benzoic acids with Aspergillus flavus.

Aromatic carboxylic acids are readily obtained from lignin in biomass processing facilities. However, efficient technologies for lignin valorization are missing. In this work, a microbial screening was conducted to find versatile biocatalysts capable of transforming several benzoic acids structurally related to lignin, employing vanillic acid as model substrate. The wild-type Aspergillus flavus growing cells exhibited exquisite selectivity towards the oxidative decarboxylation product, 2-methoxybenzene-1,4-diol. Interestingly, when assaying a set of structurally related substrates, the biocatalyst displayed the oxidative removal of the carboxyl moiety or its reduction to the primary alcohol whether electron withdrawing or donating groups were present in the aromatic ring, respectively. Additionally, A. flavus proved to be highly tolerant to vanillic acid increasing concentrations (up to 8 g/L), demonstrating its potential application in chemical synthesis. A. flavus growing cells were found to be efficient biotechnological tools to perform self-sufficient, structure-dependent redox reactions. To the best of our knowledge, this is the first report of a biocatalyst exhibiting opposite redox transformations of the carboxylic acid moiety in benzoic acid derivatives, namely oxidative decarboxylation and carboxyl reduction, in a structure-dependent fashion.

Structure elucidation and antioxidant activity of a novel polysaccharide from Polyporus umbellatus sclerotia

A novel water-soluble polysaccharide PUP60S2, with a molecular weight of 1.44×104Da, was obtained from the sclerotia of Polyporus umbellatus by hot water extraction, ethanol precipitation, anion-exchange and size-exclusion chromatography. PUP60S2 was a polysaccharide comprised of about 22.3% glucuronic acid. Monosaccharide composition analysis showed that PUP60S2 was only comprised of glucose and glucuronic acid. Reduction of carboxyl groups, sugar analysis, methylation analysis, together with one and two dimension NMR spectra disclosed that the backbone of PUP60S2 consisted of (1→6)-β-d-glucopyranosyl, every second of which was substituted at O-3 by side chains consisting of terminal β-d-Glcp, (1→3)-β-d-Glcp, (1→3)-β-d-GlcpA, (1→4)-β-d-Glcp and (1→4)-β-d-GlcpA units. The antioxidant activity assay in vitro showed that PUP60S2 exerted a significant scavenging effect on DPPH, hydroxyl radical and superoxide radical in a dose-dependent manner.

Occurrence of sulfated fucose branches in fucosylated chondroitin sulfate are essential for the polysaccharide effect preventing muscle damage induced by toxins and crude venom from Bothrops jararacussu snake.

Snake envenoming is an important public health problem around the world, particularly in tropics. Beyond deaths, morbidity induced by snake venoms, such as myotoxicity, is of pivotal consequence to population. Bothrops jararacussu is the main venomous snake in southeast region of Brazil, and particularly presents strong myotoxic effect. The only available therapy, antibothropic antivenom, poorly affects venom-induced myotoxicity. The aim of this study is to assess the ability of fucosylated chondroitin sulfate (fucCS), a glycosaminoglycan with anticoagulant and antithrombotic properties, and its derivatives to inhibit toxic activities of B. jararacussu crude venom and its isolated toxins, named bothropstoxins (BthTX-I and BthTX-II). The in vitro myotoxic activities induced by crude venom, by BthTX-I alone and by toxins together were abolished by fucCS. Carboxyl reduction (fucCS-CR) kept this ability whereas defucosilation (defucCS) abrogates myoprotection. We observed the same pattern in the response of these polysaccharides in antagonizing the increase in plasma creatine kinase (CK) levels, the reduction of skeletal muscle CK content and the rise of myeloperoxidase (MPO) activity induced by crude venom and isolated toxins. FucCS inhibited edematogenic activity and partially prevented the reduction of total leukocytes in blood when pre-incubated with crude venom. Furthermore, the venom procoagulant effect was completely antagonized by increasing concentrations of fucCS, although this polyanion could stop neither the tail bleeding nor the skin hemorrhage induced by Bothrops jararaca venom. The B. jararacussu phospholipase, hyaluronidase, proteolytic and collagenase activities were inhibited in vitro. The results suggest that fucCS could be able to interact with both toxins, and it is able to inhibit BthTX-II phospholipase activity. Light microscopy of extensor digitorum longus muscle (EDL) muscle showed myoprotection by fucCS, once necrotic areas, edema and inflammatory cells were all decreased as compared to venom injection alone. Altogether, data show that fucCS was able to inhibit myotoxicity and inflammation induced by B. jararacussu venom and its phospholipase toxins, BthTX-I and BthTX-II. Thus, fucosylated chondroitin sulfate is a new polyanion with potential to be used as an adjuvant in the treatment of snakebites in the future.

Microbial transformations of antimicrobial quinolones and related drugs

The quinolones are an important group of synthetic antimicrobial drugs used for treating bacterial diseases of humans and animals. Microorganisms transform antimicrobial quinolones (including fluoroquinolones) and the pharmacologically related naphthyridones, pyranoacridones, and cinnolones to a variety of metabolites. The biotransformation processes involve hydroxylation of methyl groups; hydroxylation of aliphatic and aromatic rings; oxidation of alcohols and amines; reduction of carboxyl groups; removal of methyl, carboxyl, fluoro, and cyano groups; addition of formyl, acetyl, nitrosyl, and cyclopentenone groups; and cleavage of aliphatic and aromatic rings. Most of these reactions greatly reduce or eliminate the antimicrobial activity of the quinolones.

Location and fate of carboxyl groups in aspen alkaline peroxide-impregnated chemithermomechanical pulp fibres during alkaline peroxide bleaching

The origin and kinetic changes of carboxyl groups in aspen chemithermomechanical pulp (CTMP) fibres during alkaline peroxide bleaching were evaluated. The results showed that the major contributors of carboxyl groups in aspen CTMP fibres were the 4-O-methylglucuronic acid, galacturonic acid and the carboxyl groups in oxidized lignin. Alkaline peroxide bleaching could increase the total carboxyl groups, surface charge and dissolved anionic substances. However, the excess degradation by superfluous hydroxide and peroxide could result in the reduction of carboxyl groups in fibres because of the production and dissolution of low-molar-mass substances. The total carboxyl groups from polysaccharides in fibres remained constant, and the increase of carboxyl groups in fibres should result from the carboxyl groups newly formed by the lignin oxidation during peroxide bleaching. Alkaline peroxide bleaching could also result in the removal of a large part of extractives and a small fraction of lignin on the fibre surface.

Thermodynamic constraints shape the structure of carbon fixation pathways

Thermodynamics impose a major constraint on the structure of metabolic pathways. Here, we use carbon fixation pathways to demonstrate how thermodynamics shape the structure of pathways and determine the cellular resources they consume. We analyze the energetic profile of prototypical reactions and show that each reaction type displays a characteristic change in Gibbs energy. Specifically, although carbon fixation pathways display a considerable structural variability, they are all energetically constrained by two types of reactions: carboxylation and carboxyl reduction. In fact, all adenosine triphosphate (ATP) molecules consumed by carbon fixation pathways – with a single exception – are used, directly or indirectly, to power one of these unfavorable reactions. When an indirect coupling is employed, the energy released by ATP hydrolysis is used to establish another chemical bond with high energy of hydrolysis, e.g. a thioester. This bond is cleaved by a downstream enzyme to energize an unfavorable reaction. Notably, many pathways exhibit reduced ATP requirement as they couple unfavorable carboxylation or carboxyl reduction reactions to exergonic reactions other than ATP hydrolysis. In the most extreme example, the reductive acetyl coenzyme A (acetyl-CoA) pathway bypasses almost all ATP-consuming reactions. On the other hand, the reductive pentose phosphate pathway appears to be the least ATP-efficient because it is the only carbon fixation pathway that invests ATP in metabolic aims other than carboxylation and carboxyl reduction. Altogether, our analysis indicates that basic thermodynamic considerations accurately predict the resource investment required to support a metabolic pathway and further identifies biochemical mechanisms that can decrease this requirement.

Chemical reduction of carboxyl groups in heparin abolishes its vasodilatory activity

Previous studies have shown that heparin induces vascular relaxation via integrin-dependent nitric oxide (NO)-mediated activation of the muscarinic receptor. The aim of this study was to identify the structural features of heparin that are necessary for the induction of vasodilatation. To address this issue, we tested heparin from various sources for their vasodilatation activities in the rat aorta ring. Structural and chemical characteristics of heparin, such as its molecular weight and substitution pattern, did not show a direct correlation with the vasodilation activity. Principal component analysis (PCA) of circular dichroism (CD), (1)H-nuclear magnetic resonance (NMR) and vasodilation activity measurements confirmed that there is no direct relationship between the physico-chemical nature and vasodilation activity of the tested heparin samples. To further understand these observations, unfractionated heparin (UFH) from bovine intestinal mucosa, which showed the highest relaxation effect, was chemically modified. Interestingly, non-specific O- and N-desulfation of heparin reduced its anticoagulant, antithrombotic, and antihemostatic activities, but had no effect on its ability to induce vasodilation. On the other hand, chemical reduction of the carboxyl groups abolished heparin-induced vasodilation and reduced the affinity of heparin toward the extracellular matrix (ECM). In addition, dextran and dextran sulfate (linear non-sulfated and highly sulfated polysaccharides, respectively) did not induce significant relaxation, showing that the vasodilation activity of polysaccharides is neither charge-dependent nor backbone unspecific. Our results suggest that desulfated heparin molecules may be used as vasoactive agents due to their low side effects.

Glucuronoxylomannan from Cryptococcus neoformans Down-regulates the Enzyme 6-Phosphofructo-1-kinase of Macrophages

The encapsulated yeast Cryptococcus neoformans is the causative agent of cryptococosis, an opportunistic life-threatening infection. C. neoformans is coated by a polysaccharide capsule mainly composed of glucuronoxylomannan (GXM). GXM is considered a key virulence factor of this pathogen. The present work aimed at evaluating the effects of GXM on the key glycolytic enzyme, 6-phosphofructo-1-kinase (PFK). GXM inhibited PFK activity in cultured murine macrophages in both dose- and time-dependent manners, which occurred in parallel to cell viability decrease. The polysaccharide also inhibited purified PFK, promoting a decrease on the enzyme affinity for its substrates. In macrophages GXM and PFK partially co-localized, suggesting that internalized polysaccharide directly may interact with this enzyme. The mechanism of PFK inhibition involved dissociation of tetramers into weakly active dimers, as revealed by fluorescence spectroscopy. Allosteric modulators of the enzyme able to stabilize its tetrameric conformation attenuated the inhibition promoted by GXM. Altogether, our results suggest that the mechanism of GXM-induced cell death involves the inhibition of the glycolytic flux.

Study on anti-metastasis of heparin derivatives as ligand antagonist of p-selectin

Heparin has a potential value as therapeutic agents that block P-selectin-mediated cell adhesion and prevent tumor metastasis. However, the strong anticoagulant potency limits its applicability for the anti-metastasis activity. Carboxyl and sulfate groups of heparin are closely related to its anticoagulant activity, so seven kinds of heparin derivatives related to carboxyl and sulfate groups were prepared, and their effects on anti-metastasis as ligand antagonist of p-selectin were studied. The results showed that heparin, carboxyl reduction heparin, 2-O-desulfated heparin and N-desulfated- N-acetylated heparin could inhibit the adhesion of tumor cells to endothelial cells and platelets effectively as ligand antagonist of P-selectin.

Isolation and characterization of poly- and oligosaccharides from the red microalga Porphyridium sp.

The current study forms part of an ongoing research effort focusing on the elucidation of the chemical structure of the sulfated extracellular polysaccharide of the red microalga Porphyridium sp. (UTEX 637). We report here on the chemical structure of a fraction separated from an acidic crude extract of the polysaccharide, as investigated by methylation analysis, carboxyl reduction–methylation analysis, desulfation–methylation analysis, partial acid hydrolysis, Smith degradation, together with 1D and 2D 1H and 13C NMR spectroscopy. This fraction with a molar mass of 2.39 × 10 5 g mol −1 comprised d- and l-Gal, d-Glc, d-Xyl, d-GlcA, and sulfate groups in a molar ratio of 1.0:1.1:2.1:0.2:0.7. The almost linear backbone of the fraction is composed of (1→2)- or (1→4)-linked d-xylopyranosyl, (1→3)-linked l-galactopyranosyl, (1→3)-linked d-glucopyranosyl, and (1→3)-linked d-glucopyranosyluronic acid and comprises a possible acidic building unit: [(2 or 4)-β- d-Xyl p-(l→3)] m -α- d-Glc p-(1→3)-α- d-Glc pA-(1→3)- l-Gal p(l→ Attached to the backbone are sulfate groups and nonreducing terminal d-xylopyranosyl and galactopyranosyl residues, which occur at the O-6 positions of Glc-derived moieties in the main chain.

A sulfated glucuronofucan containing both fucofuranose and fucopyranose residues from the brown alga Chordaria flagelliformis

A fucoidan fraction composed of l-fucose, sulfate, and d-glucuronic acid in a molar proportion of about 1:1:0.25 and small amount of acetyl groups was isolated from the brown alga Chordaria flagelliformis. Several modified polysaccharides were prepared from the native fucoidan using solvolytic desulfation, carboxyl reduction, and partial acid hydrolysis. Polysaccharide structures were elucidated by methylation analysis and 1D and 2D NMR spectroscopy. The fucoidan was shown to contain a backbone of 3-linked α- l-fucopyranose residues, about one-third of which are glycosylated at C-2 by α- d-glucopyranosyluronic acid residues. About half of the latter residues are glycosylated at C-4 by single α- l-fucofuranose residues or by disaccharides α- l-Fuc f-(1→2)-α- l-Fuc f-(1→. Fucofuranose residues are mono- and disulfated at different positions, whereas some additional sulfate groups occupy C-2 and C-4 of the backbone, the latter position being also partially acetylated.

Free Radical Conformations and Conversions in X-Irradiated Single Crystals of l-Cysteic Acid by Electron Magnetic Resonance and Density Functional Theory Studies

Single crystals of L-cysteic acid monohydrate were X-irradiated and studied at 295 K using EPR, ENDOR, and EIE techniques. Three spectroscopically different radicals were observed. These were a deamination radical reduction product (R1), and two oxidation products formed by hydrogen abstraction (radicals R2, R3). R2 and R3 were shown to exhibit the same chemical structure while exhibiting very different geometrical conformations. Cluster DFT calculations at the 6-31G(d,p) level of theory supported the experimental observations for radicals R1 and R2. It was not possible to simulate the R3 radical in any attempted cluster; hence, for this purpose a single molecule approach was used. The precursor radicals for R1, R2, and R3, identified in the low-temperature work on L-cysteic acid monohydrate by Box and Budzinski, were also investigated using DFT calculations. The experimentally determined EPR parameters for the low-temperature decarboxylated cation could only be reproduced correctly within the cluster when the carboxyl group remained in the proximity of the radical. Only one of the two observed low-temperature carboxyl anions (stable at 4 and 48 K) could be successfully simulated by the DFT calculations. Evidence is presented in support of the conclusions that the carboxyl reduction product already is protonated at 4 K and that the irreversible conversion between the two reduction products is brought forward by an umbrella-type inversion of the carboxyl group.