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Constitutive Host Resistance
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
The first event in the series of events which constitute the respiratory burst is the activation of the oxidase that catalyzes the transfer of one or two electrons from NADPH to oxygen and results in the formation of superoxide and hydrogen peroxide. During the course of this reaction, highly reactive oxygen intermediates are formed. These are superoxide ions, peroxide ions and hydroxyl radicals. Singlet oxygen has two unoccupied electron orbits in its outer valence orbit. It is the reduction of oxygen by the acquisition of electrons in this outer valence orbit that produces the superoxide ions and peroxide ions. The hydroxyl radicals are formed by the Haber-Weiss or Fenton reaction when the superoxide ions react with hydrogen peroxide in the presence of iron or copper.
Iron, Oxygen Stress, and The Preterm Infant
Published in Bo Lönnerdal, Iron Metabolism in Infants, 2020
Singlet oxygen is formed if the spin of one of the unpaired electrons of oxygen is changed in a way that permits oxygen to react with a nonradical (Table 1). Singlet oxygen is, therefore, a very reactive species. Formation of singlet oxygen has been recognized if porphyrins are exposed to visible light12 and in the lens and the retina of the mammalian eye.13
Influence of Air on Essential Oil Constituents
Published in K. Hüsnü Can Başer, Gerhard Buchbauer, Handbook of Essential Oils, 2020
Darija Gajić, Gerhard Buchbauer
It represents the reaction between the excited singlet state of oxygen molecule 1O2 and an allylic hydrogen atom (Figure 29.3). This results in shifting the double bond to a position adjacent to the original double bond; that is, an allylic hydroperoxide is formed. Notably, the direct excitation (transition of the ground state oxygen 3O2 by light to a singlet form) is highly unlikely. Hence, singlet oxygen (unlike almost all molecules) is uncommon in a standard environment and its excitation usually requires a certain sensitizing molecule.
Apoferritin: a potential nanocarrier for cancer imaging and drug delivery
Published in Expert Review of Anticancer Therapy, 2021
Hanitrarimalala Veroniaina, Xiuhua Pan, Zhenghong Wu, Xiaole Qi
PDT is an emerging treatment modality that is under intensive clinical investigations for many types of disease due to its noninvasive medical treatment and limited side effects. This method consists of using photosensitizers that generate singlet oxygen as a cytotoxic agent under light irradiation to treat diseases including cancer. However, selective delivery of photosensitizers to tumors remains a problem. Interestingly, apoferritin as an innate tumor-targeting nanocarrier offers a hollow cavity to accommodate successful PDT. Several potent photosensitizer molecules have been reported to be encapsulated within the apoferritin proteins, including methylene blue, Hypocrellin B (HB), rose Bengal (RB), and zinc hexadecafluorophthalocyanine (ZnF16Pc). Chuanshan’s group has worked extensively on the effect of HB as a natural photosensitizer [85]. This biomaterial isolated from Hypocrella bambusea suffers from poor water solubility, low bioavailability, and poor tumor selectivity which limit its application. To improve the photodynamic activity of HB, this compound was encapsulated within apoferritin nanocarriers. The study revealed that HB trapping in the apoferritin cavity significantly increased its solubility and the HB-apoferritin can be considered as a potential photosensitive drug for tumors targeting photodynamic therapy.
Nano Antiviral Photodynamic Therapy: a Probable Biophysicochemical Management Modality in SARS-CoV-2
Published in Expert Opinion on Drug Delivery, 2021
Khatereh Khorsandi, Sepehr Fekrazad, Farshid Vahdatinia, Abbas Farmany, Reza Fekrazad
Fullerene and its derivatives could potentially demonstrate antiviral activity, which has strong impacts on the HIV-infection treatment. The fullerene derivatives antiviral activity is due to many biological properties such as their unique molecular architecture and antioxidant activity. It has been displayed that fullerene derivatives could inhibit and make a complex with HIV protease [68,69]. Dendrofullerene 1 has demonstrated the largest anti-protease activity [70–72]. Derivative 2, the trans-2 isomer, is a potential inhibitor of HIV-1 replication. Water-insoluble fullerene (C60) derivatives have antiviral activity on enveloped viruses. After visible-light illumination for 5 h of semliki forest virus (SFV, Togaviridae) or vesicular stomatitis virus (VSV, Rhabdoviridae)(79). In the presence of C60, the infectivity of these viruses is missed. This effect is attributed to the production of singlet oxygen and is equally efficient in solutions that contained proteins. Various dyes could produce singlet oxygen generation [73]. The examination that fullerenes and its derivatives do not have an immunogenetic effect further endorses their possibility as pharmaceutical compounds.
Insights and controversies on sunscreen safety
Published in Critical Reviews in Toxicology, 2020
Juliana P. Paiva, Raiane R. Diniz, Alvaro C. Leitão, Lucio M. Cabral, Rodrigo S. Fortunato, Bianca A. M. C. Santos, Marcelo de Pádula
It is proposed that photosensitization reactions, which may be type I or type II, are initiated by the interaction of the UV photon with endogenous chromophores in their ground state, inducing photoexcitability of these molecules that become sensitizing mediators, namely photoexcited state intermediate (Wondrak et al. 2006; Cadet et al. 2009, 2015; Schuch et al. 2017). The first step of the type I reaction involves a complex chain of events that initiates with energy transfer from the photoexcited state, most often the triplet state of the sensitizer, directly to substrate molecules in a one-electron transfer reaction. In the presence of oxygen, these reactions culminate in ROS generation such as the superoxide anion radical (O2•–) which can rapidly undergo dismutation into hydrogen peroxide (H2O2). In its turn, H2O2 can be reduced by transition metals, such as ferrous and cuprous ions, through Fenton reaction, leading to hydroxyl radical (•OH) generation. In type II reaction, the energy of the photosensitizer is transferred directly to an oxygen molecule, which results in the formation of singlet oxygen (1O2), leading to subsequent oxidation of surrounding biomolecules (Wondrak et al. 2006; Cadet et al. 2009, 2015; Baptista et al. 2017).