Comparative Study of Spectral and Functional Properties of Wild Type and Double Mutant H(L173)L/I(L177)H Reaction Centers of the Purple Bacterium .

Previously, we found that in the reaction center (RC) of the purple bacterium , formation of heterodimeric primary electron donor (P) caused by the substitution of His-L173 by Leu, was compensated by the second mutation Ile-L177 - His. Significant changes in the spectral properties, pigment composition, and redox potential of P observed in the H(L173)L RC, are restored to the corresponding characteristics of the native RC in the RC H(L173)L/I(L177)H, with the difference that the energy of the long-wavelength Q optical transition of P increases significantly (by ~75 meV). In this work, it was shown using light-induced difference FTIR spectroscopy that the homodimeric structure of P is preserved in the RC with double mutation with partially altered electronic properties: electronic coupling in the radical-cation of the P dimer is weakened and localization of the positive charge on one of its halves is increased.

Anomalous Temperature Dependence of the Triplet-Triplet Energy Transfer in I(L177)H Mutant Reaction Centers.

In photosynthetic reaction centers, quenching of the primary donor triplet state by energy transfer to the carotenoid molecule provides efficient suppression of generation of singlet-excited oxygen, potent chemical oxidant. This process in the reaction centers is thermoactivated, and discontinues at temperatures below 40 K. In these reaction centers, substitution of amino acid residue isoleucine at the 177 position of the L-subunit with histidine results in the sharp decrease of activation energy, so that the carotenoid triplets are populated even at 10 K.

Evaluation of Five Screening Tools in Detecting Physical Frailty in Cirrhosis and Their Prognostic Role.

: Physical frailty (PF) is a syndrome of decreased physical function and reserves, preventing patients from coping with stressful events. PF screening tools in patients with liver cirrhosis (LC) can help evaluate the risk of complications and death. The aim of this study was to assess the performance of five screening tools in detecting PF and their ability to predict 18-month mortality in LC.

Evaluation of parameters influencing the quality of colon preparation with a split-dose regimen of sulfate salts.

Background: Bowel cleansing is an important factor for the quality of colonoscopy. We aimed to evaluate the efficacy of split-dose oral sulfate salts on bowel preparation and to determine parameters influencing the quality of bowel cleaning.

Method: Consecutive adults who completed their preparation for colonoscopy with a regimen of sulfate salts were enrolled.

Serial rotational thromboelastometry measurements show worsening hypocoagulability in acute-on-chronic liver failure and are associated with the severity of liver disease.

Background: Viscoelastic tests are used to better understand the complex picture of hemostasis in cirrhosis. Limited data exist regarding the clinical relevance of rotational thromboelastometry (ROTEM) in acute-on-chronic liver failure (ACLF) or acute decompensation (AD). We examined the pattern and role of sequential observations of 9 ROTEM components in both ACLF and AD groups.

Role of hydrogen-bond networks on the donor side of photosynthetic reaction centers from purple bacteria.

For the last decades, significant progress has been made in studying the biological functions of H-bond networks in membrane proteins, proton transporters, receptors, and photosynthetic reaction centers. Increasing availability of the X-ray crystal and cryo-electron microscopy structures of photosynthetic complexes resolved with high atomic resolution provides a platform for their comparative analysis. It allows identifying structural factors that are ensuring the high quantum yield of the photochemical reactions and are responsible for the stability of the membrane complexes.

A combination of clot formation abnormalities in thromboelastometry has a high prognostic value in patients with acute-on-chronic liver failure.

Background: Global coagulation tests offer a better tool to assess procoagulant and anticoagulant pathways, fibrinolysis and clot firmness and evaluate more accurately coagulation defects compared to conventional coagulation tests. Their prognostic role in acute-on-chronic liver disease (ACLF) or acute decompensation (AD) has not been well established.

Aims: To assess the properties and prognostic value of the coagulation profile measured by rotational thromboelastometry (ROTEM) in ACLF and AD.

Mechanisms of sarcopenia in liver cirrhosis and the role of myokines.

Sarcopenia is a syndrome characterized by a decline in skeletal muscle quantity and/or quality, strength and performance, leading to unfortunate events, such as injurious falls or even death. It is not identical to frailty and malnutrition, even though there is a significant overlap among these syndromes. In patients with liver cirrhosis (LC), sarcopenia is classified as secondary and has been associated with increased morbidity and mortality during the pre- and post-transplantation period.

The Presence of Myosteatosis Is Associated with Age, Severity of Liver Disease and Poor Outcome and May Represent a Prodromal Phase of Sarcopenia in Patients with Liver Cirrhosis.

Background/aims: Myosteatosis implies impaired muscle quality. The aim of the study was to investigate the association of myosteatosis with other muscle abnormalities and its role in the prognosis of liver cirrhosis (LC).

Method: Skeletal muscle index (SMI) and myosteatosis were measured by computed tomography.

Properties and Crystal Structure of the Photosynthetic Reaction Center with Double Amino Acid Substitution I(L177)H + F(M197)H.

The photosynthetic reaction center of the purple bacterium with two site-directed mutations Ile-L177-His and M197 Phe-His is of double interest. The substitution I(L177)H results in strong binding of a bacteriochlorophyll molecule with L-subunit. The second mutation F(M197)H introduces a new H-bond between the C2-acetyl carbonyl group of the bacteriochlorophyll P and His-M197, which is known to enhance the stability of the complex.

Stabilization of Photosynthetic Reaction Center by the Introduction of Disulfide Bonds.

The photosynthetic reaction center of the purple nonsulfur bacterium is a useful model for the study of mechanisms of photoinduced electron transfer and a promising component for photo-bio-electrocatalytic systems. The basic research and technological applications of this membrane pigment-protein complex require effective approaches to increase its structural stability. In this work, a rational design approach to genetically modify the reaction centers by introducing disulfide bonds is used.

HFA-PEFF score as an independent predictor of 2-year mortality in liver cirrhosis patients.

Background And Aims: Cardiovascular complications of liver cirrhosis include high cardiac output heart failure with reduced afterload and diastolic dysfunction. Heart Failure Association Pre-test assessment, Echocardiography and natriuretic peptide, Functional testing, Final etiology (HFA-PEFF) (values 0-6) is a diagnostic tool for heart failure. It is a cluster of echocardiographic and biochemical parameters.

Serum troponin is elevated in acute decompensation and acute-on-chronic liver failure and is associated with severity of liver disease and short-term mortality.

Background: The role of high sensitive cardiac Troponin (hs-cTn) in patients with liver cirrhosis (LC) and liver-related acute events is not well established.

Aim: To assess the prognostic performance of hs-cTn I in acute decompensation (AD) and acute-on-chronic liver failure (ACLF).

Methods: Two cohorts of consecutive patients, a derivation (retrospective) and a validation (prospective), were evaluated and 30-day-mortality was recorded.

Properties of Mutant Photosynthetic Reaction Centers of Purple Non-Sulfur Bacteria Cereibacter sphaeroides with M206 Ile→Gln Substitution.

In the structure of photosynthetic reaction center (RC) of the purple bacterium Cereibacter sphaeroides the highly conserved amino acid residue Ile-M206 is located near the bacteriochlorophyll dimer P, which is the primary electron donor, and the monomeric bacteriochlorophyll B, which is the nearest electron acceptor. Since Ile-M206 is close to the C2-acetyl group of bacteriochlorophyll P, the hydroxyl group of Tyr-M210, and to the C9-keto group of bacteriochlorophyll B, as well as to the water molecule near the latter group, this site can be used for introducing mutations in order to study mechanisms of primary photochemical processes in the RC. Previously it was shown that the Ile→Glu substitution at the M204 position (analog of M206 in the RC of C.

In memory of Vladimir Anatolievich Shuvalov (1943-2022): an outstanding biophysicist.

We present here a tribute to one of the foremost biophysicists of our time, Vladimir Anatolievich Shuvalov, who made important contributions in bioenergetics, especially on the primary steps of conversion of light energy into charge-separated states in both anoxygenic and oxygenic photosynthesis. For this, he and his research team exploited pico- and femtosecond transient absorption spectroscopy, photodichroism & circular dichroism spectroscopy, light-induced FTIR (Fourier-transform infrared) spectroscopy, and hole-burning spectroscopy. We remember him for his outstanding leadership and for being a wonderful mentor to many scientists in this area.

X-ray structure of the reaction center with an M197 Phe→His substitution clarifies the properties of the mutant complex.

The first steps of the global process of photosynthesis take place in specialized membrane pigment-protein complexes called photosynthetic reaction centers (RCs). The RC of the photosynthetic purple bacterium , a relatively simple analog of the more complexly organized photosystem II in plants, algae and cyanobacteria, serves as a convenient model for studying pigment-protein interactions that affect photochemical processes. In bacterial RCs the bacteriochlorophyll (BChl) dimer P serves as the primary electron donor, and its redox potential is a critical factor in the efficient functioning of the RC.

Bacterial DNA is a prognostic factor for mortality in patients who recover from spontaneous bacterial peritonitis.

Background: Spontaneous bacterial peritonitis (SBP) is associated with a high mortality. The aim was to investigate whether bacterial deoxyribonucleic acid (bactDNA) could offer an accurate identification of pathogens and to explore its prognostic role during and early after an SBP episode.

Methods: Consecutive patients with SBP (SBP-group) and patients with decompensated cirrhosis without SBP/bacterascites (control-group) were enrolled.

Myostatin in combination with creatine phosphokinase or albumin may differentiate patients with cirrhosis and sarcopenia.

In patients with liver cirrhosis (LC), sarcopenia is correlated with frequent complications and increased mortality. Myostatin, a myokine, is a potential biomarker of skeletal mass and/or sarcopenia. The aim of this study was to examine the association between myostatin and muscle mass and evaluate myostatin as a biomarker of sarcopenia in LC.

Effect of Detergents and Osmolytes on Thermal Stability of Native and Mutant Rhodobacter sphaeroides Reaction Centers.

Photosynthetic reaction center (RC) of the purple bacterium Rhodobacter sphaeroides is one of the most well-studied transmembrane pigment-protein complexes. It is a relatively stable protein with established conditions for its isolation from membranes, purification, and storage. However, it has been shown that some amino acid substitutions can affect stability of the RC, which results in a decrease of the RCs yield during its isolation and purification, disturbs spectral properties of the RCs during storage, and can lead to sample heterogeneity.

New Approaches to the Treatment of Chronic Hepatitis B.

The currently recommended treatment for chronic hepatitis B virus (HBV) infection achieves only viral suppression whilst on therapy, but rarely hepatitis B surface antigen (HBsAg) loss. The ultimate therapeutic endpoint is the combination of HBsAg loss, inhibition of new hepatocyte infection, elimination of the covalently closed circular DNA (cccDNA) pool, and restoration of immune function in order to achieve virus control. This review concentrates on new antiviral drugs that target different stages of the HBV life cycle (direct acting antivirals) and others that enhance both innate and adaptive immunity against HBV (immunotherapy).