The Evaluation of Objective and Subjective Fate of Teeth in the Mandible Fracture Line and the Management-A Center's Experience.

OBJECTIVE: The decision to retain or extract teeth in the line of mandibular fractures has been a subject of debate in much of the scientific literature, and there is a need for further evidence to clear this issue. Thus, the aim of this study was to investigate both the positive and negative effects of teeth in the line of mandibular fractures provide more evidence in this field, as well as take into consideration patients' quality of life after the surgery. METHODS: Patients after trauma with teeth in the line of mandibular fractures were included in this study. Open reduction and rigid internal fixation, elastic intermaxillary reduction were expected to achieve a satisfactory occlusion and/or anatomical reduction in the fragments as assessed by orthopantomogram, computed tomography scans, and clinical examination. The remaining cases had maxillomandibular fixation (MMF) with an arch bar and bridle wire. All the patients included in this study will take the Visual Analog Scale score evaluation before and after surgery subjectively to further verify the impact on their life qualify, as well as the further treatment needed. RESULTS: A total of 78 patients with teeth in the line of mandibular fractures were included in this study. Open reduction and rigid internal fixation was used in 37 patients, whereas another 35 patients accepted elastic intermaxillary reduction. Six cases underwent MMF. The number of involved teeth was 83. Three of the 83 teeth involved in the fracture lines healed with complications. In the cases where the teeth had been removed before fracture treatment, or in cases of delayed extractions, no complications were noted. The majority of the patients felt good about the whole treatment, however, 4 in the MMF group complained about worry about their oral health due to MMF leading to mouth open limitation. CONCLUSION: The factors that should be considered for removal include the condition of the teeth and alveolar bone, the timing and the type of treatment, as well as the patients' desire, if possible. This is an individual-based decision that needs to consider more objective and subjective potential risks to avoid complications.

BdFAR4, a root-specific fatty acyl-coenzyme A reductase, is involved in fatty alcohol synthesis of root suberin polyester in Brachypodium distachyon.

Suberin is a complex hydrophobic polymer of aliphatic and phenolic compounds which controls the movement of gases, water, and solutes and protects plants from environmental stresses and pathogenic infection. The synthesis and regulatory pathways of suberin remain unknown in Brachypodium distachyon. Here we describe the identification of a B. distachyon gene, BdFAR4, encoding a fatty acyl-coenzyme A reductase (FAR) by a reverse genetic approach, and investigate the molecular relevance of BdFAR4 in the root suberin synthesis of B. distachyon. BdFAR4 is specifically expressed throughout root development. Heterologous expression of BdFAR4 in yeast (Saccharomyces cerevisiae) afforded the production of C20:0 and C22:0 fatty alcohols. The loss-of-function knockout of BdFAR4 by CRISPR/Cas9-mediated gene editing significantly reduced the content of C20:0 and C22:0 fatty alcohols associated with root suberin. In contrast, overexpression of BdFAR4 in B. distachyon and tomato (Solanum lycopersicum) resulted in the accumulation of root suberin-associated C20:0 and C22:0 fatty alcohols, suggesting that BdFAR4 preferentially accepts C20:0 and C22:0 fatty acyl-CoAs as substrates. The BdFAR4 protein was localized to the endoplasmic reticulum in Arabidopsis thaliana protoplasts and Nicotiana benthamiana leaf epidermal cells. BdFAR4 transcript levels can be increased by abiotic stresses and abscisic acid treatment. Furthermore, yeast one-hybrid, dual-luciferase activity, and electrophoretic mobility shift assays indicated that the R2R3-MYB transcription factor BdMYB41 directly binds to the promoter of BdFAR4. Taken together, these results imply that BdFAR4 is essential for the production of root suberin-associated fatty alcohols, especially under stress conditions, and that its activity is transcriptionally regulated by the BdMYB41 transcription factor.

Efficacy and safety of mitoxantrone hydrochloride liposome injection in Chinese patients with advanced breast cancer: a randomized, open-label, active-controlled, single-center, phase II clinical trial.

PURPOSE: This trial aimed to evaluate the efficacy and safety of mitoxantrone hydrochloride liposome injection (Lipo-MIT) in advanced breast cancer (ABC). METHODS: In this randomized, open-label, active-controlled, single-center, phase II clinical trial, eligible patients were randomized in a ratio of 1:1 to receive Lipo-MIT or mitoxantrone hydrochloride injection (MIT) intravenously. The primary endpoint was objective response rate (ORR). The secondary endpoints were disease control rate (DCR), progression-free survival (PFS), and safety outcomes. RESULTS: Sixty patients were randomized to receive Lipo-MIT or MIT. The ORR was 13.3% (95% confidence interval (CI): 3.8-30.7%) for Lipo-MIT and 6.7% (95% CI: 0.8-22.1%) for MIT. The DCR was 50% (95% CI: 31.3-68.7%) with Lipo-MIT vs. 30% (95% CI: 14.7-49.4%) with MIT. The median PFS was 1.92 months (95% CI: 1.75-3.61) for Lipo-MIT and 1.85 months (95% CI: 1.75-2.02) for MIT. The most common toxicity was myelosuppression. Lipo-MIT resulted in an incidence of 86.7% of leukopenia and 80.0% of neutropenia, which was marginally superior to MIT (96.7% and 96.7%, respectively). Lipo-MIT showed a lower incidence of cardiovascular events (13.3% vs. 20.0%) and increased cardiac troponin T (3.3% vs. 36.7%); but higher incidence of anemia (76.7% vs. 46.7%), skin hyperpigmentation (66.7% vs. 3.3%), and fever (23.3% vs. 10.0%) than MIT. Conclusions The clinical benefit parameters of Lipo-MIT and MIT were comparable. Lipo-MIT provided a different toxicity profile, which might be associated with the altered distribution of the drug. Additional study is needed to elucidate the potential benefit of Lipo-MIT in ABC. CLINICAL TRIAL REGISTRATION: This study is registered with ClinicalTrials.gov (No. NCT02596373) on Nov 4, 2015.

Molecular Composition of Size-Fractionated Fulvic Acid-Like Substances Extracted from Spent Cooking Liquor and Its Relationship with Biological Activity.

The treatment of spent cooking liquor is critical for clean production of pulp and paper industry. There is a compelling need to develop a cost-effective and green technology for reuse of organic matter in spent cooking liquor to mitigate the negative impacts on the environment. The objective of this study is to examine the chemical structure of fulvic acid-like substances extracted from spent cooking liquor (PFA) and their relationship with bioactivity in plant growth. Compared with the benchmark Pahokee peat fulvic acid (PPFA), PFA has less aromatic structure, but higher content of lignin, carbohydrates, and amino acid. After fractionation, protein/amino proportion decreased with increasing molecular weight, but the aromaticity increased. Under salt stress, rice seedling growth was promoted by PFA with low molecular weight (<5 kDa), but inhibited by fraction with high molecular weight (>10 kDa). Principal component analysis suggested that promoted growth was more related with chemical structure (O- and N-alkyl moieties) than with molecular weight. This study provided the theoretical basis for development of an innovative green technology of sustainable reuse of spent cooking liquor in agriculture.

Reconstruction of Deep Circumflex Iliac Artery Free Flap for Multiple Recurrent Ameloblastoma in Mandible.

Ameloblastoma is the most common odontogenic tumor of epithelial origin. These tumors are benign in nature but have a high rate of recurrence and possible malignant development when treated inadequately. However, recurrent ameloblastomas in bone grafts are rare. This article presents a rare case of a multiple recurrent ameloblastoma, with the last recurrence in a nonvascularized free iliac bone graft of the mandible, reconstructed with vascularized deep circumflex iliac artery free flap for the surgical defect. Furthermore, an updated review of the literature on recurrent ameloblastomas affecting the bone graft is provided.

Advantages with prophylactic PEG-rhG-CSF versus rhG-CSF in breast cancer patients receiving multiple cycles of myelosuppressive chemotherapy: an open-label, randomized, multicenter phase III study.

BACKGROUND: PEG-rhG-CSF reduces neutropenia and improves chemotherapy safety. In China's registration trial (CFDA: 2006L01305), we assessed its efficacy and safety against rhG-CSF, and prospectively explored its value over multiple cycles of chemotherapy. METHODS: In this open-label, randomized, multicenter phase 3 study, breast cancer patients (n = 569) were randomized to receive PEG-rhG-CSF 100 µg/kg, PEG-rhG-CSF 6 mg, or rhG-CSF 5 µg/kg/d after chemotherapy. The primary endpoints were the incidence and duration of grade 3/4 neutropenia during cycle 1. Secondary endpoints included the incidence and duration of grade 3/4 neutropenia during cycles 2-4, the incidence of febrile neutropenia, and the safety. RESULTS: A once-per-cycle PEG-rhG-CSF at either 100 µg/kg or 6 mg was not different from daily injections of rhG-CSF for either incidence or duration of grade 3/4 neutropenia. Interestingly, a substantial difference was noted during cycle 2, and the difference became bigger over cycles 3-4, reaching a statistical significance at cycle 4 in either incidence (P = 0.0309) or duration (P = 0.0289) favoring PEG-rhG-CSF. A significant trend toward a lower incidence of all-grade adverse events was noted at 129 (68.98%), 142 (75.53%), and 160 (82.47%) in the PEG-rhG-CSF 100 µg/kg and 6 mg and rhG-CSF groups, respectively (P = 0.0085). The corresponding incidence of grade 3/4 drug-related adverse events was 2/187 (1.07%), 1/188 (0.53%), and 8/194 (4.12%), respectively (P = 0.0477). Additionally, PFS in metastatic patients preferred PEG-rhG-CSF to rhG-CSF despite no significance observed by Kaplan-Meier analysis (n = 49, P = 0.153). CONCLUSIONS: PEG-rhG-CSF is a more convenient and safe formulation and a more effective prophylactic measure in breast cancer patients receiving multiple cycles of chemotherapy.

In Situ Hydrogel Conditioning of Tissue Samples To Enhance the Drug's Sensitivity in Ambient Mass Spectrometry Imaging.

Ion suppression from the tissue matrix has a severe effect on the mass spectrometry imaging (MSI) of drugs. This problem hinders further applications of MSI in preclinical drug research and development. In this study, an in situ hydrogel conditioning method was developed to enhance the sensitivity of air-flow-assisted desorption electrospray ionization (AFADESI)-MSI. Instead of the traditional washing or digestion treatment in solvent, this method used a solid phase hydrogel to "wash" tissue sections. It was demonstrated that this in situ hydrogel conditioning method improved the drug signal by as much as 2- to 25-fold in MSI, especially for hydrophobic compounds. Furthermore, the obvious dislocation of analytes was not observed. The evaluation of spatial resolution indicated that the amount of dislocation in tissue sections with the hydrogel process was less than the resolution of AFADESI-MSI. The underlying reasons for the MSI signal enhancement were initially investigated. The decreased signal intensities of choline, betaine, and carnitine and the increased intensities of the [M + H]+/[M + Na]+ and [M + H]+/[M + K]+ ratios for drugs in the mass spectra of pretreated tissues provided evidence that this method can reduce the levels of highly competitive quaternary ammonium and inorganic salts in the tissues. The preformation of a thin liquid film for droplet pickup would also raise the ionization efficiency of drugs. These results demonstrated that this in situ hydrogel conditioning method provides a rapid and feasible approach to improving the sensitivity of ambient MSI for drug mapping in tissues.

Differences of circular RNA expression profiles between monozygotic twins' blood, with the forensic application in bloodstain and saliva.

Monozygotic twins (MZTs) possess identical genomic DNA sequences and are usually indistinguishable through routine forensic DNA typing methods, which can be relevant in criminal and paternity cases. Recently, novel epigenetic methods involving DNA methylation and microRNA analysis have been introduced to differentiate MZTs. In this study, we explore the potential of using epigenetic markers, specifically circular RNAs (circRNAs), a type of non-coding RNA (ncRNA), to identify MZTs, and investigate the unique expression patterns of circRNAs within pairs of MZTs, enabling effective differentiation. Epigenetics regulates gene expression at the post-transcriptional level and plays a crucial role in cell growth and aging. CircRNAs, a recently characterized subclass of ncRNA, have a distinct covalent loop structure without the typical 5' cap or 3' tail. They have been reported to modulate various cellular processes and play roles in embryogenesis and eukaryotic development. To achieve this, we conducted a comprehensive circRNA sequencing analysis (circRNA-seq) using total RNA extracted from the blood samples of five pairs of MZTs. We identified a total of 15,257 circRNAs in all MZTs using circRNA-seq. Among them, 3, 21, 338, and 2967 differentially expressed circRNAs (DEcircRNAs) were shared among five, four, three, and two pairs of MZTs, respectively. Subsequently, we validated twelve selected DEcircRNAs using real-time quantitative polymerase chain reaction (RT-qPCR) assays, which included hsa_circ_0004724, hsa_circ_0054196, hsa_circ_004964, hsa_circ_0000591, hsa_circ_0005077, hsa_circ_0054853, hsa_circ_0054716, hsa_circ_0002302, hsa_circ_0004482, hsa_circ_0001103, novel_circ_0030288 and novel_circ_0056831. Among them, hsa_circ_0005077 and hsa_circ_0004482 exhibited the best performance, showing differences in 7 out of 10 pairs of MZTs. These twelve differentially expressed circRNAs also demonstrated strong discriminative power when tested on saliva samples from 10 pairs of MZTs. Notably, hsa_circ_0004724 displayed differential expression in 8 out of 10 pairs of MZTs in their saliva. Additionally, we evaluated the detection sensitivity, longitudinal temporal stability, and suitability for aged bloodstains of these twelve DEcircRNAs in forensic scenarios. Our findings highlight the potential of circRNAs as molecular markers for distinguishing MZTs, emphasizing their suitability for forensic application.

Cytochrome c polymerization by successive domain swapping at the C-terminal helix.

Cytochrome c (cyt c) is a stable protein that functions in a monomeric state as an electron donor for cytochrome c oxidase. It is also released to the cytosol when permeabilization of the mitochondrial outer membrane occurs at the early stage of apoptosis. For nearly half a century, it has been known that cyt c forms polymers, but the polymerization mechanism remains unknown. We found that cyt c forms polymers by successive domain swapping, where the C-terminal helix is displaced from its original position in the monomer and Met-heme coordination is perturbed significantly. In the crystal structures of dimeric and trimeric cyt c, the C-terminal helices are replaced by the corresponding domain of other cyt c molecules and Met80 is dissociated from the heme. The solution structures of dimeric, trimeric, and tetrameric cyt c were linear based on small-angle X-ray scattering measurements, where the trimeric linear structure shifted toward the cyclic structure by addition of PEG and (NH(4))(2)HPO(4). The absorption and CD spectra of high-order oligomers (approximately 40 mer) were similar to those of dimeric and trimeric cyt c but different from those of monomeric cyt c. For dimeric, trimeric, and tetrameric cyt c, the DeltaH of the oligomer dissociation to monomers was estimated to be about -20 kcal/mol per protomer unit, where Met-heme coordination appears to contribute largely to DeltaH. The present results suggest that cyt c polymerization occurs by successive domain swapping, which may be a common mechanism of protein polymerization.

From natural environment to animal tissues: A review of microplastics(nanoplastics) translocation and hazards studies.

Microplastics (MPs) and nanoplastic (NPs) pollution is a global concern due to the massive use of plastic products. Although there have been many studies on the treatments of animals with MPs/NPs, there are few systematic summaries of MPs/NPs translocation and hazards in animals. This review comprehensively summarizes the pathways by which animals are exposed to MPs/NPs in the environment, in particular, to summarize in detail their translocation and hazards in vivo. Studies have shown that MPs/NPs enter the animals' body through water, food, breath and even skin, enter the blood circulation through the lungs and digestive tract, and eventually accumulate in various tissues. After a summary of the studies, we found a high correlation between the tissue accumulation of MPs/NPs and their particle size, with 4-20 µm MPs appearing to be more prone to accumulate in tissues. These MPs/NPs accumulated in animal tissues may be transferred to humans through the food chain. Thus, we summarized the studies on the accumulation of MPs/NPs in livestock and poultry products, showing that MPs/NPs in livestock and poultry products gradually increased with the complexity of processing and packaging processes. There are few reports related to direct contamination of livestock products by MPs/NPs, we hope that this review will bring together the growing body of evidence that MPs/NPs can directly harm human health through the food chain.

Analysis of the correlation between malocclusion, bad oral habits, and the caries rate in adolescents.

BACKGROUND: Malocclusion deformity and caries are common oral diseases in adolescents. In order to explore the correlation between malocclusion deformity and caries prevalence in adolescents, this study analyzed the influence of factors such as poor oral habits on caries in adolescents. METHODS: In this study, 1,093 adolescents aged 11 to 14 enrolled in 2-3 schools in Zhangjiakou area from September 2020 to June 2021 were selected as the research subjects. The basic data of these adolescents were collected by questionnaires. Malocclusion and caries were examined by on-site inspection. Their bad oral habits were also investigated. After data collection, the chi-square test, logistic regression, the Mann-Whitney U test, and the Kruskal-Wallis H test were used for multivariate analysis. RESULTS: The results showed that the incidence of malocclusion was 72.66% and the caries rate was 68.8% among adolescents aged 11-14 in this area. The 4 bad oral habits of biting, mandibular protrusion, lateral chewing, and mouth breathing were the influencing factors of malocclusion in adolescents. Bad oral habits, malocclusion, and frequent consumption of sugary beverages were independent risk factors for caries in adolescents, and significantly positively correlated with the caries rate. CONCLUSIONS: Malocclusion and the four bad oral habits were independent risk factors of caries in adolescents.

Characterization of polyvinyl alcohol/starch composite films incorporated with p-coumaric acid modified chitosan and chitosan nanoparticles: A comparative study.

In this paper, polyvinyl alcohol/starch composite films with p-coumaric acid modified chitosan (P-CS) and chitosan nanoparticles (P-CSNPs) at different concentrations were successfully prepared. The films were compared for their mechanical, thermal, physical, antioxidant, antibacterial, cytotoxicity and optical barrier properties. The results suggested that P-CS could significantly increase the tensile strength (TS) of the film from 15.67 MPa to a maximum of 24.32 MPa. The compact structure of P-CSNPs film prevented water diffusion, reducing the water amount within. Both films showed a reduction in water solubility, the extent of swelling, and water vapor transmittance. Specifically, P-CSNPs films showed better thermal stability while P-CS films revealed higher antioxidant activity. Besides, the P-CS films exhibited excellent transparency and good ultraviolet-barrier at 200-280 nm. P-CSNPs films demonstrated higher antibacterial activity on both Gram-negative and Gram-positive bacteria. Additionally, P-CS films were less cytotoxic compared to P-CSNPs films.

Effects of forage source and particle size on chewing activity, ruminal pH, and saliva secretion in lactating Holstein cows.

The present study investigated the effects of dietary forage source (quality) and particle size on chewing activity, saliva secretion, and ruminal pH. Twelve multiparous lactating Holstein cows, four of which were ruminally cannulated, were used in a replicated 4 × 4 Latin square experimental design with a 2 × 2 factorial arrangement of treatments. Cows fed wild-rye hay diets had longer daily eating times than cows fed oaten hay diets. Treatments had no effect on ruminating time; therefore, resting time varied inversely to eating time. Neither the rate nor the amount of saliva secretion while eating, ruminating, or resting was affected by diet, resulting in similar total daily saliva secretions across treatments (231 L/day). Total volatile fatty acids (VFAs) in the ruminal fluid from animals fed oaten hay diets were higher than those from animals fed wild-rye hay diets; further, VFAs increased with decreasing forage particle size (FPS). Consistent with elevated VFA concentrations, reducing FPS and including oaten hay in the diet decreased mean ruminal pH and increased the daily time of ruminal pH under 5.8. Results of this study suggest that forage source and particle size affect ruminal pH might be via variations in VFA production rather than increased salivary recycling of buffering substrates.

Activation of fulvic acid-like in paper mill effluents using H2O2/TiO2 catalytic oxidation: Characterization and salt stress bioassays.

Increasing environmental concerns about organic waste in paper mill effluents demand alternative wastewater management technology. We reported novel activation of fulvic acid-like in paper mill effluents using hydrogen peroxide (H2O2) as oxidizer and titanium oxide (TiO2) as catalyst. Spectroscopic characteristics of fulvic acid-like in paper mill effluents before and after activation (PFA and PFA-Os, respectively) were compared with a benchmark fulvic acid extracted from leonardite (LFA). Results indicated that PFA-Os exhibited less lignin structures, more functional groups and lower molecular weight than PFA, sharing much similarity with LFA. Among PFA-Os with varying degrees of oxidation, PFA-O-3 activated with 1:2 vol ratio of paper mill effluent and 30% H2O2 for 20 min digestion at 90 °C stands out to be the optimal for further examination of its biological activity. Bioassays with rice seed/seedling indicated that applications of LFA at 2-5 mg-C/L and PFA-O-3 at 60-100 mg-C/L significantly increased rice seed germination rate and seedling growth under salt stress imposed with 100 mM NaCl. The mechanism was mainly through reduced oxidative damage via activation of antioxidative enzymes and lipid peroxidation. This study provides the needed technical basis of safer and cleaner technologies for innovative management of paper mill effluents.

Magnetic-Sensitive Nanoparticle Self-Assembled Superhydrophobic Biopolymer-Coated Slow-Release Fertilizer: Fabrication, Enhanced Performance, and Mechanism.

Although commercialized slow-release fertilizers coated with petrochemical polymers have revolutionarily promoted agricultural production, more research should be devoted to developing superhydrophobic biopolymer coatings with superb slow-release ability from sustainable and ecofriendly biomaterials. To inform the development of the superhydrophobic biopolymer-coated slow-release fertilizers (SBSF), the slow-release mechanism of SBSF needs to be clarified. Here, the SBSF with superior slow-release performance, water tolerance, and good feasibility for large-scale production was self-assembly fabricated using a simple, solvent-free process. The superhydrophobic surfaces of SBSF with uniformly dispersed Fe3O4 superhydrophobic magnetic-sensitive nanoparticles (SMNs) were self-assembly constructed with the spontaneous migration of Fe3O4 SMNs toward the outermost surface of the liquid coating materials ( i.e., pig fat based polyol and polymethylene polyphenylene isocyanate in a mass ratio 1.2:1) in a magnetic field during the reaction-curing process. The results revealed that SBSF showed longer slow-release longevity (more than 100 days) than those of unmodified biopolymer-coated slow-release fertilizers and excellent durable properties under various external environment conditions. The governing slow-release mechanism of SBSF was clarified by directly observing the atmosphere cushion on the superhydrophobic biopolymer coating using the synchrotron radiation-based X-ray phase-contrast imaging technique. Liquid water only contacts the top of the bulges of the solid surface (10.9%), and air pockets are trapped underneath the liquid (89.1%). The atmosphere cushion allows the slow diffusion of water vapor into the internal urea core of SBSF, which can decrease the nutrient release and enhance the slow-release ability. This self-assembly synthesis of SBSF through the magnetic interaction provides a strategy to fabricate not only ecofriendly biobased slow-release fertilizers but also other superhydrophobic materials for various applications.

Effects of chelated Zn/Cu/Mn on redox status, immune responses and hoof health in lactating Holstein cows.

To evaluate the effects of chelated Zn/Cu/Mn on redox status, immune responses and hoof health in lactating Holstein cows, 48 head in early lactation were divided into healthy or lame groups according to their gait score. Cows were fed the same amount of Zn/Cu/Mn as sulfate salts or in chelated forms for 180 days, and foot-and-mouth disease (FMD) vaccine was injected at day 90. The results showed that lame cows had lower antioxidant function, serum Zn/Mn levels, hair Cu levels, and hoof hardness. Moreover, increased antioxidant status, FMD antibody titers, serum and hair levels of Zn/Cu/Mn, and hoof hardness and decreased milk fat percent and arthritis biomarkers were observed in cows fed chelated Zn/Cu/Mn. In summary, supplementation with chelated Zn/Cu/Mn improved antioxidant status and immune responses, reduced arthritis biomarkers, and increased accumulation of Zn/Cu/Mn in the body and hoof hardness in dairy cows.

Adsorption of water-soluble dyes onto modified resin.

Adsorption behavior of five kinds of water-soluble dyes onto functionalized resin NKY has been dynamically and thermodynamically investigated. The results showed that the adsorption rates of dye K-GN, K-2BP, KN-R, AAB and 2G are all controlled by liquid film diffusion and particle diffusion. Equilibrium adsorption data can be well described by three-parameter equation. The first layer adsorption is the physical enhanced by chemical effect but multilayer adsorption is typically physical adsorption. Standard free energy change DeltaG(0) and standard entropy change DeltaS(0) indicate the adsorption of the dyes onto NKY can occur spontaneously.

Self-oxidation of cytochrome c at methionine80 with molecular oxygen induced by cleavage of the Met-heme iron bond.

Met80 of cytochrome c (cyt c) has been shown to dissociate from its heme iron when cyt c interacts with cardiolipin (CL), which triggers the release of cyt c into the cytosol initiating apoptosis. We found that the mass of human cyt c increases by 16 Da in the Met80-Lys86 region by reaction with molecular oxygen in the presence of CL-containing liposomes and dithiothreitol (DTT). To investigate the effect of Met80 dissociation on the reaction of cyt c with molecular oxygen without affecting its secondary structures, a human cyt c mutant (Δ8384 cyt c) was constructed by removing two amino acids (Val83 and Gly84) from the loop containing Met80. According to MALDI-TOF-MS and tandem mass measurements, Met80 of Δ8384 cyt c was modified site-specifically to methionine sulfoxide when purified in the presence of molecular oxygen, whereas Met80 was not modified in the absence of molecular oxygen. A red-shift of the Soret band from 406 to 412 nm and absorption increase at ∼536 and ∼568 nm were observed for Δ8384 cyt c when it reacted with DTT and molecular oxygen, followed by a further red-shift of the Soret band to 416 nm and absorption increase at ∼620 and ∼650 nm. These results indicate that Met80 of cyt c is oxidized site-specifically by formation of the oxy and subsequent compound I-like species when Met80 dissociates from the heme iron, where the Met80 modification may affect its peroxidase activity related to apoptosis.