Efficacy and safety of proxalutamide (GT0918) in severe or critically ill patients with COVID-19: study protocol for a prospective, open-label, single-arm, single-center exploratory trial

BACKGROUND

The rapid worldwide spread of COVID-19 has caused a global health challenge with high mortality of severe or critically ill patients with COVID-19. To date, there is no specific efficient therapeutics for severe or critically ill patients with COVID-19. It has been reported that androgen is related to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Proxalutamide as an androgen receptor antagonist has shown potential treatment effects on COVID-19 patients. Thus, this trial is designed to investigate the efficacy and safety of proxalutamide in severe or critically ill patients with COVID-19.

METHODS

This single-arm, open-label, single-center prospective exploratory trial is planned to recruit 64 severe or critically ill patients with COVID-19 in China. Recruitment started on 16 May 2022 and is foreseen to end on 16 May 2023. Patients will be followed-up until 60 days or death, whichever comes first. The primary outcome is the 30-day all-cause mortality. Secondary endpoints included 60-day all-cause mortality, rate of clinical deterioration within 30 days after administration, time to sustain clinical recovery (determined using an 8-point ordinal scale), mean change in the Acute Physiology and Chronic Health Evaluation II scores, change in oxygenation index, changes in chest CT scan, percentage of patients confirmed negative for SARS-CoV-2 by nasopharyngeal swab, change in Ct values of SARS-CoV-2 and safety. Visits will be performed on days 1 (baseline), 15 or 30, 22, and 60.

DISCUSSION

The trial is the first to investigate the efficacy and safety of proxalutamide in severe or critically ill patients with COVID-19. The findings of this study might lead to the development of better treatment for COVID-19 and provide convincing evidence regarding the efficacy and safety of proxalutamide.

TRIAL REGISTRATION

This study was registered on 18 June 2022 at the Chinese Clinical Trial Registry (ChiCTR2200061250).

Ginger supplement significantly reduced length of hospital stay in individuals with COVID-19

BACKGROUND

Evidence from previous studies has suggested that ginger extract exhibits the potential as an alternative treatment for Coronavirus disease 2019 (COVID-19). Here, we want to investigate whether ginger supplement improves the clinical manifestation of hospitalized COVID-19 individuals.

METHODS

A total of 227 hospitalized individuals with COVID-19 were randomized to either the control (n = 132) or intervention group (n = 95). The intervention group took ginger supplement orally at the dosage of 1.5 g twice daily, until they were discharged from the hospital. Both groups received the same standard of general medical care during hospitalization, and the length of stay was recorded and compared between groups.

RESULTS

Among all participants, a significant reduction in hospitalization time (the difference between the treatment and control groups was 2.4 d, 95% CI 1.6-3.2) was detected in response to the ginger supplement. This effect was more pronounced in men, participants aged 60 years or older, and participants with pre-existing medical conditions, relative to their counterparts (P-interactions < 0.05 for all).

CONCLUSION

Ginger supplement significantly shortened the length of stay of hospitalized individuals with COVID-19.

TRIAL REGISTRATION

The trial was registered on the Chinese Clinical Trial Registry (ChiCTR2200059824).

Ginsenoside Rb1 Reduces D-GalN/LPS-induced Acute Liver Injury by Regulating TLR4/NF-κB Signaling and NLRP3 Inflammasome

BACKGROUND AND AIMS

The effect of ginsenoside Rb1 on D-galactosamine (D-GalN)/lipopolysaccharide (LPS)-induced acute liver injury (ALI) is unknown. The aim of this study was to evaluate the effect of ginsenoside Rb1 on ALI and its underlying mechanisms.

METHODS

Mice were pretreated with ginsenoside Rb1 by intraperitoneal injection for 3 days before D-GalN/LPS treatment, to induce ALI. The survival rate was monitored every hour for 24 h, and serum biochemical parameters, hepatic index and histopathological analysis were evaluated to measure the degree of liver injury. ELISA was used to detect oxidative stress and inflammatory cytokines in hepatic tissue and serum. Immunohistochemistry staining, RT-PCR and western blotting were performed to evaluate the expression of toll-like receptor 4 (TLR4), nuclear factor-kappa B (NF-κB), and NLR family, pyrin domain-containing 3 protein (NLRP3) in liver tissue and Kupffer cells (KCs).

RESULTS

Ginsenoside Rb1 improved survival with D-GalN/LPS-induced ALI by up to 80%, significantly ameliorated the increased alanine and aspartate transaminase, restored the hepatic pathological changes and reduced the levels of oxidative stress and inflammatory cytokines altered by D-GalN/LPS. Compared to the control group, the KCs were increased in the D-GalN/LPS groups but did not increase significantly with Rb1 pretreatment. D-GalN/LPS could upregulate while Rb1 pretreatment could downregulate the expression of interleukin (IL)-1β, IL-18, NLRP3, apoptosis associated speck-like protein containing CARD (ASC) and caspase-1 in isolated KCs. Furthermore, ginsenoside Rb1 inhibited activation of the TLR4/NF-κB signaling pathway and NLRP3 inflammasome induced by D-GalN/LPS administration.

CONCLUSIONS

Ginsenoside Rb1 protects mice against D-GalN/LPS-induced ALI by attenuating oxidative stress and the inflammatory response through the TLR4/NF-κB signaling pathway and NLRP3 inflammasome activation.

Ulinastatin ameliorates LPS‑induced pulmonary inflammation and injury by blocking the MAPK/NF‑κB signaling pathways in rats

Ulinastatin, a urinary trypsin inhibitor (UTI) is commonly used to treat patients with acute inflammatory disease. However, the underlying mechanisms of its anti‑inflammatory effect in acute lung injury (ALI) are not fully understood. The present study aimed to investigate the protective effect of UTI and explore its potential mechanisms by using a rat model of lipopolysaccharide (LPS)‑induced ALI. Rats were treated with 5 mg/kg LPS by intratracheal instillation. The histological changes in LPS‑induced ALI was evaluated using hematoxylin and eosin staining and the myeloperoxidase (MPO) activity was determined using ELISA. The wet/dry ratio (W/D ratio) of the lungs was used to assess the severity of pulmonary edema and Evans blue dye was used to evaluate the severity of lung vascular leakage. The results demonstrated that LPS administration induced histological changes and significantly increased the lung W/D ratio, MPO activity and Evans blue dye extravasation compared with the control group. However, treatment with UTI attenuated LPS‑induced ALI in rats by modifying histological changes and reducing the lung W/D ratio, MPO activity and Evans blue dye extravasation. In addition, LPS induced the secretion of numerous pro‑inflammatory cytokines in bronchoalveolar lavage fluid (BALF), including tumor necrosis factor‑α, interleukin (IL)‑6, IL‑1β and interferon‑γ; however, these cytokines were strongly reduced following treatment with UTI. In addition, UTI was able to reduce cellular counts in BALF, including neutrophils and leukocytes. Western blotting demonstrated that UTI significantly blocked the LPS‑stimulated MAPK and NF‑κB signaling pathways. The results of the present study indicated that UTI could exert an anti‑inflammatory effect on LPS‑induced ALI by inhibiting the MAPK and NF‑κB signaling pathways, which suggested that UTI may be considered as an effective drug in the treatment of ALI.

[Relationship between blood lactate level and the prognosis of patients with diabetic sepsis]

OBJECTIVE

To evaluate the prognostic value of blood lactate (Lac) level in sepsis patients with or without diabetes.

METHODS

106 patients admitted to intensive care unit (ICU) of Zhongshan Hospital Affiliated to Fudan University from April 2015 to November 2016 were enrolled. The patients with age > 18 years and the length of hospital stay > 24 hours were included. Records including blood Lac, serum creatinine (SCr), white blood cell count (WBC), platelet count (PLT), sequential organ failure assessment (SOFA) on the first day of admission; minimum oxygen index (PaO₂/FiO₂) in 3 days after admission; mechanical ventilation, whether there was a history of diabetes, usage of biguanides, etiology control treatment, usage of continuous renal replacement therapy (CRRT) were collected. According to the level of blood Lac patients were divided into high Lac group (Lac > 2 mmol/L) and low Lac group (Lac ≤ 2 mmol/L); based on their diabetic history, sepsis patients were divided into the diabetes group and non-diabetes group. The survival curve of each group was analyzed by Kaplan-Meier regression analysis, and the factors influencing the prognosis were analyzed by multivariate Cox regression analysis.

RESULTS

There were 76 males and 30 females sepsis patients, with an average age of (68.1±14.7) years old. In the 51 patients of low Lac group, there were 7 patients who suffered from diabetes. While in the 55 patients of high Lac group, there were 12 patients who suffered from diabetes. Compared with low Lac group, high Lac group had a higher age, higher SOFA score, and a lower proportion of patients who had the treatment of etiology control (all P < 0.05). There was no significant difference of blood Lac in sepsis patients with diabetes and those without diabetes (mmol/L: 3.03±2.73 vs. 2.81±2.40, P > 0.05). Kaplan-Meier survival curve analysis showed that the 90-day survival rate in the high Lac group was significantly lower than that in the low Lac group (56.36% vs. 90.20%, χ ² = 0.697, P = 0.008). The high Lac group without diabetes had lower survival rate, and the 90-day survival rate was significantly lower than that of the low Lac group without diabetes (58.14% vs. 90.90%, χ ² = 7.152, P = 0.007); there was no significant difference in 90-day survival rate between the high Lac group and the low Lac group with diabetes (50.00% vs. 85.71%, χ ² = 0.012, P = 0.914). Multivariate Cox regression analysis showed that blood Lac was an independent risk factor for the prognosis of sepsis patients [odds ratio (OR) = 3.863, 95% confidence interval (95%CI) = 1.237-12.060, P = 0.020]. After stratification according to their diabetic history, the blood Lac was an independent risk factor for the prognosis of sepsis patients without diabetes (OR = 4.816, 95%CI = 1.407-15.824, P = 0.010), but the blood Lac had no effect on the prognosis of sepsis patients with diabetes (OR = 0.000, 95%CI = 0.000-1.103, P = 0.270).

CONCLUSIONS

The predictive value of blood Lac on sepsis patients with or without diabetes was different. The blood Lac was related with the prognosis of sepsis patients without diabetes, while further study should be conducted for the prognostic value of blood Lac in sepsis patients with diabetes, and it's possible to increase the cut-off-point of Lac level in these patients.

High-flow Nasal Cannula Versus Noninvasive Ventilation for Treatment of Acute Hypoxemic Respiratory Failure in Renal Transplant Recipients

OBJECTIVE

This study aimed to evaluate the outcomes of high-flow nasal cannula (HFNC) oxygen therapy compared with noninvasive ventilation (NIV) for the treatment of acute hypoxemic respiratory failure in renal transplant recipients.

METHODS

Data were retrospectively collected from a tertiary intensive care unit (ICU) from July 1, 2011, to September 31, 2015. All renal recipients who had acute respiratory failure at that period of time were classified into the HFNC or NIV group depending on the initial form of respiratory support.

RESULTS

A total of 38 patients were enrolled in this study. Twenty patients received HFNC and the other 18 received NIV as the initial respiratory support. The ICU mortality in the HFNC group was 5% (1 patient), compared with 22.2% (4 patients) in the NIV group (P = .083). The median length of the ICU stay was 12 days in the HFNC group, compared with 14 days in the NIV group (P = .297). The number of ventilator-free days at day 28 was significantly higher in the HFNC group than in the NIV group (26 ± 3 vs 21 ± 3; P < .001). The incidences of both pneumothorax (0% vs 22.2%; P = .042) and skin breakdown (0% vs 22.2%; P = .042) were significantly lower in the HFNC group.

CONCLUSIONS

In renal transplant recipients with acute hypoxemic respiratory failure secondary to severe pneumonia, HFNC achieved outcomes similar to NIV. In addition, HFNC was associated with an increased number of ventilator-free days at day 28 and fewer complications.

Acute transverse myelitis of the cervical spine secondary to psoas abscess

BACKGROUND

Acute transverse myelitis is uncommon and presumably results from an autoimmune process or a preceding infection. Most cases of bacterial myelitis are due to hematogenous dissemination from urinary or respiratory tract infections or contiguous spreading from a neighboring infected structure. A psoas abscess rarely spreads to higher levels of the spinal cord. No cases of acute cervical myelitis due to a psoas abscess have been previously reported.

CASE PRESENTATION

A 34-year-old man was transferred to our hospital due to progressive muscle weakness, sensory deficits and severe hypotension. Two weeks prior to admission, he had received low back injection to relieve back pain in a healthcare clinic. One day prior to admission, his condition had worsened. On admission, he was tetraplegic with absence of sensation below the level of the suprasternal fossa. A lumbar CT scan demonstrated an abscess in the left psoas, and the magnetic resonance imaging (MRI) scan of the entire spinal suggested a cervical spine infection. A cerebrospinal fluid (CSF) analysis performed before surgery indicated the possibility of bacterial infection. An operation was performed to drain the abscess. Microbiological cultivation revealed a Methicillin-resistant Staphylococcus aureus (MRSA) infection. The patient was administered with vancomycin for 10 days and followed by oral formulations of linezolid for 6 weeks. The patient's general condition improved, and he was successfully discharged. Six months later, a follow-up MRI revealed that the lesion of the cervical spine had been ameliorated, and the sensation and myodynamia of his upper limbs had partially recovered.

CONCLUSION

This was a rare case of a high-level cervical spine pyogenic infection complicating psoas abscess. An invasive paravertebral injection procedure was thought to be the initial damaging event that created a port of entry for MRSA into the psoas muscle and caused a subsequent psoas abscess. This case indicated that evaluation of higher levels of the spine is warranted when a psoas abscess coexists with severe weakness.

Early- and late-onset severe pneumonia after renal transplantation

BACKGROUND

The aim of this study was to clarify the distinctions in the clinical characteristics and outcomes between early- and late-onset severe pneumonia after renal transplantation requiring ICU admission.

METHODS

The data were retrospectively collected in consecutive renal recipients with severe pneumonia from January 1, 2009, to December 31, 2013, in a tertiary ICU. We classified the patients according to the time of pneumonia onset as follows: early-onset severe pneumonia (E-SP) corresponded to a pulmonary infection occurring during the first year following the transplantation, and late-onset severe pneumonia (L-SP) corresponded to a pulmonary infection occurring after the first year following the transplantation.

RESULTS

In the E-SP patients, fungi (42.1%) and viruses (31.6%) were the most common pathogens. Twenty-three (71.9%) patients received non-invasive ventilation (NIV), 15 (65.2%) of whom were intubated. The median duration of the ICU and hospital stays was 11 ± 5 and 19 ± 4 days, respectively. In the L-SP patients, bacteria (42.1%) and viruses (26.3%) were the predominant pathogens. Four of 15 (26.7%) patients failed NIV treatment. The median duration of the ICU and hospital stays was 9 ± 3 and 16 ± 3 days, respectively. The ICU mortality among the E-SP patients was 18.8% (6 of 32), compared with 7.1% (2 of 28) in the L-SP group (P = 0.264).

CONCLUSIONS

Early-onset severe pneumonia in renal transplant recipients resulted in a more serious condition, higher rate of NIV failure, longer duration of mechanical ventilation, and increased length of ICU and hospital stays.

Numerical simulations of deformation and aggregation of red blood cells in shear flow

This article reviews numerical simulations of red blood cells (RBCs) mainly using the lattice Boltzmann method (LBM), focusing on the 2-dimensional deformation and aggregation of the cells in simple shear flow. We outline the incorporation of the immersed boundary method into the LBM, in which the membrane forces are obtained from the membrane model. The RBCs are simulated as a single biconcave capsule and as a doublet of biconcave capsules. The transition from swinging to tumbling motions of the RBCs, as induced by reducing the shear rate or increasing the membrane bending stiffness, is discussed. Also discussed is the aggregation tendency of the doublet of RBCs, for which homogenous deformability maintained RBC aggregation, whereas an increased deformability difference resulted in RBC dissociation.

Pharmacological profile of phosphatidylinositol 3-kinases and related phosphatidylinositols mediating endothelin(A) receptor-operated native TRPC channels in rabbit coronary artery myocytes

BACKGROUND AND PURPOSE

Endothelin(A) (ET(A) ) receptor-operated canonical transient receptor potential (TRPC) channels mediate Ca²⁺ influx pathways, which are important in coronary artery function. Biochemical pathways linking ET(A) receptor stimulation to TRPC channel opening are unknown. We investigated the involvement of phosphatidylinositol 3-kinases (PI3K) in ET(A) receptor activation of native heteromeric TRPC1/C5/C6 and TRPC3/C7 channels in rabbit coronary artery vascular smooth muscle cells (VSMCs).

EXPERIMENTAL APPROACH

A pharmacological profile of PI3K was created by studying the effect of pan-PI3K, pan-Class I PI3K and Class I PI3K isoform-selective inhibitors on ET(A) receptor-evoked single TRPC1/C5/C6 and TRPC3/C7 channel activities in cell-attached patches from rabbit freshly isolated coronary artery VSMCs. The action of phosphatidylinositol 3-phosphate- [PI(3)P], 4-phosphate- [PI(4)P] and 5-phosphate- [PI(5)P] containing molecules involved in PI3K-mediated reactions were studied in inside-out patches. Expression of PI3K family members in coronary artery tissue lysates were analysed using quantitative PCR.

KEY RESULTS

ET(A) receptor-operated TRPC1/C5/C6 and TRPC3/C7 channel activities were inhibited by wortmannin. However, ZSTK474 and AS252424 reduced ET(A) receptor-evoked TRPC1/C5/C6 channel activity but potentiated TRPC3/C7 channel activity. All the PI(3)P-, PI(4)P- and PI(5)P-containing molecules tested induced TRPC1/C5/C6 channel activation, whereas only PI(3)P stimulated TRPC3/C7 channels.

CONCLUSIONS AND IMPLICATIONS

ET(A) receptor-operated native TRPC1/C5/C6 and TRPC3/C7 channel activities are likely to be mediated by Class I PI3Kγ and Class II/III PI3K isoforms, respectively. ET(A) receptor-evoked and constitutively active PI3Kγ-mediated pathways inhibit TRPC3/C7 channel activation. PI3K-mediated pathways are novel regulators of native TRPC channels in VSMCs, and these signalling cascades are potential pharmacological targets for coronary artery disease.

TRPC6 channels stimulated by angiotensin II are inhibited by TRPC1/C5 channel activity through a Ca2+- and PKC-dependent mechanism in native vascular myocytes

The present work investigated interactions between TRPC1/C5 and TRPC6 cation channel activities evoked by angiotensin II (Ang II) in native rabbit mesenteric artery vascular smooth muscle cells (VSMCs). In low intracellular Ca(2+) buffering conditions (0.1 mm BAPTA), 1 nm and 10 nm Ang II activated both 2 pS TRPC1/C5 channels and 15-45 pS TRPC6 channels in the same outside-out patches. However, increasing Ang II to 100 nm abolished TRPC6 activity but further increased TRPC1/C5 channel activity. Comparison of individual patches revealed an inverse relationship between TRPC1/C5 and TRPC6 channel activity suggesting that TRPC1/C5 inhibits TRPC6 channel activity. Inclusion of anti-TRPC1 and anti-TRPC5 antibodies, raised against intracellular epitopes, in the patch pipette solution blocked TRPC1/C5 channel currents but potentiated by about six-fold TRPC6 channel activity evoked by 1-100 nm Ang II in outside-out patches. Bath application of T1E3, an anti-TRPC1 antibody raised against an extracellular epitope, also increased Ang II-evoked TRPC6 channel activity. With high intracellular Ca(2+) buffering conditions (10 mm BAPTA), 10 nm Ang II-induced TRPC6 channel activity was increased by about five-fold compared to channel activity with low Ca(2+) buffering. In addition, increasing intracellular Ca(2+) levels ([Ca(2+)](i)) at the cytosolic surface inhibited 10 nm Ang II-evoked TRPC6 channel activity in inside-out patches. Moreover, in zero external Ca(2+) (0 [Ca(2+)](o)) 100 nm Ang II induced TRPC6 channel activity in outside-out patches. Pre-treatment with the PKC inhibitor, chelerythrine, markedly increased TRPC6 channel activity evoked by 1-100 nm Ang II and blocked the inhibitory action of [Ca(2+)](i) on TRPC6 channel activity. Co-immunoprecipitation studies shows that Ang II increased phosphorylation of TRPC6 proteins which was inhibited by chelerythrine, 0 [Ca(2+)](o) and the anti-TRPC1 antibody T1E3. These results show that TRPC6 channels evoked by Ang II are inhibited by TRPC1/C5-mediated Ca(2+) influx and stimulation of PKC, which phosphorylates TRPC6 subunits. These conclusions represent a novel interaction between two distinct vasoconstrictor-activated TRPC channels expressed in the same native VSMCs.

Intrahepatic splenosis mimicking hepatoma

A 54-year-old man with a past history of splenectomy some 20 years previously presented with a hepatic mass. Subsequent histopathology revealed that the mass was due to intrahepatic splenosis. The presentation of this case is discussed together with a literature review of splenosis.

Comparative study of photodynamic therapy vs. CO2laser vaporization in treatment of condylomata acuminata, a randomized clinical trial

BACKGROUND

Most conventional therapies for condylomata acuminata (CA) are traumatic and have high recurrence rates.

OBJECTIVES

To investigate the efficacy and safety of topical application of 5-aminolaevulinic acid (ALA) photodynamic therapy (PDT) for the treatment of CA.

METHODS

Sixty-five patients with CA were allocated into the treatment (ALA-PDT) group and treated with 20% ALA solution under occlusive dressing for 3 h followed by irradiation with the helium-neon laser at a dose of 100 J cm(-2) and a power of 100 mW. Another 21 CA patients were allocated into the control group and treated with the CO(2) laser. The treatment was to be repeated 1 week later if the lesion was not completely removed after the first treatment.

RESULTS

After one treatment, the complete removal rate was 95% in the ALA-PDT group and 100% in the control group. After two treatments with ALA-PDT, the complete removal rate in the treatment group was 100%. The recurrence rate for ALA-PDT group was 6.3% which was significantly lower than that in control group (19.1%, P < 0.05). Moreover, the proportion of patients with adverse effects in the ALA-PDT group (13.9%) was also significantly lower than that in control group (100%, P < 0.05). The side-effects in patients treated with ALA-PDT mainly included mild burning and/or stinging restricted to the illuminated area.

CONCLUSIONS

The present study shows that topical application of ALA-PDT is a simpler, more effective and safer therapy with a lower recurrence for treatment of CA compared with conventional CO(2) laser therapy.

Molecular identification and characterisation of the human eag2 potassium channel

We report the molecular cloning from foetal brain of the human potassium channel heag2. The cDNA encodes a protein of 988 amino acids, 73% identical to heag1. Heag2 is expressed in the brain, but is also found in a range of tissues including skeletal muscle. In oocytes, the channel is a non-inactivating outward rectifier, with dependence of activation rate on holding potential. Compared with heag1, the conductance-voltage curve for heag2 was shifted to the left, the voltage sensitivity was less, activation kinetics were different, and the sensitivity to terfenadine was lower. The heag2 channel may have important physiological roles.

Low IGF-I suppresses VEGF-survival signaling in retinal endothelial cells: direct correlation with clinical retinopathy of prematurity

Retinopathy of prematurity is a blinding disease, initiated by lack of retinal vascular growth after premature birth. We show that lack of insulin-like growth factor I (IGF-I) in knockout mice prevents normal retinal vascular growth, despite the presence of vascular endothelial growth factor, important to vessel development. In vitro, low levels of IGF-I prevent vascular endothelial growth factor-induced activation of protein kinase B (Akt), a kinase critical for endothelial cell survival. Our results from studies in premature infants suggest that if the IGF-I level is sufficient after birth, normal vessel development occurs and retinopathy of prematurity does not develop. When IGF-I is persistently low, vessels cease to grow, maturing avascular retina becomes hypoxic and vascular endothelial growth factor accumulates in the vitreous. As IGF-I increases to a critical level, retinal neovascularization is triggered. These data indicate that serum IGF-I levels in premature infants can predict which infants will develop retinopathy of prematurity and further suggests that early restoration of IGF-I in premature infants to normal levels could prevent this disease.

[Study on the technological process of including volatile oil of Baizhu with beta-cyclodextrin]

The volatile oil of Baizhu was included with beta-CD. The factors affecting the formation of the inclusion compounds were researched by L9(3(4)) orthogonal test. The ratio of the oil in inclusion compounds and recovery of inclusion compounds were used as criteria in the test. The best conditions for inclusion were A2B3C1, that is, the compounds should be formed in the aqueous solution containing beta-CD and oil with a raio of 8:1, aqua destillate and beta-CD with a ratio of 4:1 for two hours.

Enantioseparations by capillary electrophoresis using chiral glycosidic surfactants. I. Evaluation of cyclohexyl-pentyl-beta-D-maltoside surfactant

Chiral cyclohexyl-pentyl-beta-D-maltoside (CYMAL-5) surfactant was evaluated in the enantioseparation of charged racemic species by capillary electrophoresis. CYMAL-5 is a glycosidic surfactant (GS) with a chiral maltose polar head group and a cyclohexyl-pentyl hydrophobic tail. At concentrations above its critical micellar concentration (CMC), CYMAL-5 produces neutral micelles in aqueous media. The neutral micelles migrate at the velocity of the electroosmotic flow (EOF). As expected, the CYMAL-5 system was only useful for the enantioseparation of charged chiral solutes. The enantioresolution of the CYMAL-5 can be manipulated over a wide range of electrolyte composition, e.g., pH, ionic strength and surfactant concentration. In the presence of EOF, and in all cases, there is an optimum surfactant concentration for maximum enantioresolution, which is located at low surfactant concentration for strongly hydrophobic solutes and at high surfactant concentration for relatively hydrophilic solutes. The presence of an optimum surfactant concentration for maximum enantioresolution is attributed to the EOF. At low pH values where the EOF is negligible, enantioresolution increased with increasing surfactant concentration in the useful concentration range in a way similar to chromatography.

Activation of chicken liver dihydrofolate reductase by urea and guanidine hydrochloride is accompanied by conformational change at the active site

It has been reported that the activation of dihydrofolate reductase (DHFR) from L1210 mouse leukaemia cells by KCl or thiol modifiers is accompanied by increased digestibility by proteinases [Duffy, Beckman, Peterson, Vitols and Huennekens (1987) J. Biol. Chem. 262, 7028-7033], suggesting a loosening up of the general compact structure of the enzyme. In the present study, the peptide fragments liberated from the chicken liver enzyme by digestion with trypsin in dilute solutions of urea or guanidine hydrochloride (GuHCl) have been separated by FPLC and sequenced. The sequences obtained are unique when compared with the known sequence of DHFR and thus allow the points of proteolytic cleavage identified for the urea- and GuHCl-activated enzyme to be at or near the active site. It was also indicated by the enhanced fluorescence of 2-p-toluidinylnaphthalene 6-sulfonate that conformational changes at the active site in dilute GuHCl parallel GuHCl activation. The above results indicate that the activation of DHFR in dilute denaturants is accompanied by a loosening up of its compact structure especially at or near the active site, suggesting that the flexibility at its active site is essential for the full expression of its catalytic activity.

Activation of chicken liver dihydrofolate reductase in concentrated urea solutions

The activation and inactivation of dihydrofolate reductase from chicken liver during denaturation in a wide concentration range of urea are compared with changes in intrinsic fluorescence. At 2 M urea the enzyme is activated 3.6-fold and is stable up to 12 h in the activated form. At 4 M urea, the enzyme activity increases about 5-fold initially but the activated enzyme loses activity rapidly to a level well below that of the native enzyme. The activated enzyme is stabilized in presence of either DHF or NADPH. The Kd and Km of the enzyme for the substrates at various urea concentrations were determined and compared. In the presence of 3 M urea, the values of Kd for DHF and NADPH increase 4-fold and 10-fold, respectively, whereas the corresponding Km values increase 25-fold and 3-fold. A large increase in Vmax is mainly responsible for the activation. The inactivation and unfolding in urea are both biphasic processes. For the fast phase, the rate constant of inactivation is 10-fold greater than that of unfolding in 4 M urea. The effect of (NH4)2SO4 on the activation and unfolding of the enzyme was also studied. The results suggest that the active site of the enzyme is more easily perturbed by denaturants; and the activated enzyme appears to have a more open and flexible conformation at the active site, which is favorable for the full expression of the catalytic power of the enzyme. A scheme for the sequential activation and inactivation of DHFR accompanying its unfolding by increasing concentrations of urea is proposed.

The changes of circular dichroism and fluorescence spectra, and the comparison with inactivation rates of angiotensin converting enzyme in guanidine solutions

The circular dichroism (CD) spectrum of angiotensin converting enzyme (peptidyl-dipeptide hydrolase, EC 3.4.15.1) in the ultraviolet region was shown to have down negative peaks at 208 and 222 nm, indicating its peptide chain has an alpha-helical structure. The conformational changes of the enzyme during denaturation in guanidine solutions of increasing concentration, for 24 h at 4 degrees C, were associated with the disappearance of the two negative peaks of the CD spectra, less alpha-helical structure to various extents, a decrease in intensity of the intrinsic protein fluorescence, a red shift in the emission maximum at 340 nm and an increase in the band-width of the spectrum delta lambda. Together these findings demonstrate unfolding of the folded peptide chain of angiotensin converting enzyme and consequent exposure of its aromatic amino acid residues during denaturation. The rates of ellipticity (theta 220) changes of the enzyme during denaturation were less than those of the decrease in fluorescence intensity, demonstrating that the rate of degradation of its secondary structure was slower than that of its tertiary structure. Both the rates of inactivation and conformational change of the enzyme increased with increasing guanidine concentrations, within the range of 1.0-3.0 M. The enzyme inactivation had separate fast and slow processes. Both the rates and the extents of inactivation were much faster and larger than those of conformational changes. Compared with other enzymes, therefore, the angiotensin converting enzyme molecule appears to have a stable spatial structure, but its active site conformation is relatively unstable during denaturation.

Number of ways of joining SH groups to form multi-peptide chain proteins

The expression for the total number of isomeric structures formed upon oxidation of SH groups has previously been correctly obtained for single chain proteins only. Expressions have now been obtained for molecules consisting of 2 and 4 peptide chains of the types A2 and A2B2. The latter type is particularly important as exemplified by the immunoglobulins and the insulin receptor. For the oxidation of insulin A chain with 4 SH groups, the total number of isomeric A2 structures is 59--this is different to all the values previously reported. Lack of consideration of symmetry problems probably accounts for the erroneous results obtained by earlier workers for the number of ways of randomly joining two identical chains. The total number of isomeric structures formed from the oxidation of two light and two heavy chains with 5 and 11 SH groups respectively of the human immunoglobulin GI has been found to be 4.8 X 10(16).