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Biomedical subjects

E Jakobsson

Publications and source records attributed to E Jakobsson.

At least 19 recordsLinked to original sources

Physiological predictors of performance in cross-country skiing from treadmill tests in male and female subjects.

In order to study which parameter that best corresponds to performance during cross-country skiing, seven male and nine female cross-country skiers were tested with treadmill tests. Parameters measured or computed by metabolic gas measurements were the anaerobic threshold (AT), threshold of decompensated metabolic acidosis (TDMA), the exercise intensity where the Respiratory exchange ratio reaches 1.0 (R = 1) and peak oxygen (O2) uptake (VO2peak). Onset of blood lactate accumulation (OBLA, 4 mmol.l-1 blood lactate) was also measured. The various parameters were measured in percentage of maximal heart rate, percentage of peak O2 uptake, VO2 ml.kg-1.min-1, VO2 ml.min-1.kg-2/3 and VO2 l.min-1. Results from four large competitions were also collected to rank the subjects. With correlation analysis, it was revealed that in male subjects a high OBLA was associated with good ranking results (r = (-0.829) - (-0.964); P < 0.05-0.001). In female subjects, the best association with competition results was found for R = 1 (r = (-0.715) - (-0.810); P < 0.05). Concerning VO2 measurements, for male subjects the unit l.min-1 is suggested to be used and for female subjects either the units l.min-1, ml.min-1.kg-2/3, or ml.kg-1.min-1 could be used when predicting performance in cross-country skiing. In conclusion, treadmill tests can be used for the prediction of performance in cross-country skiing. Further, various parameters from treadmill tests in men and women are best used as predictors of performance in cross-country skiing.

Acidosis↗

A brominated flame retardant, 2,2',4,4',5-pentabromodiphenyl ether: uptake, retention, and induction of neurobehavioral alterations in mice during a critical phase of neonatal brain development.

Polybrominated diphenyl ethers (PBDEs) are used in large quantities as flame retardant additives. In a recent study, we have seen that neonatal exposure to some brominated flame retardants can cause permanent aberrations in spontaneous motor behavior that seem to worsen with age. In view of an increasing amount of PBDEs in mother's milk and in the environment, the present study was undertaken to investigate whether there is a critical and limited phase, during neonatal life, for induction of persistent neurotoxic effects of 2,2',4,4',5-pentaBDE (PBDE 99). Neonatal NMRI male mice were exposed on day 3, 10, or 19 to 8 mg 2,2',4,4',5-pentaBDE/kg body weight. Uptake and retention of 2,2',4,4',5-penta[(14)C]BDE were studied in the mouse brain after exposure to 1.5 M becquerel (Bq) 2,2',4,4',5-penta[(14)C]BDE /kg body weight (bw) on postnatal day 3, 10, or 19. Spontaneous motor behavior was observed in 4-month-old mice. Mice exposed to 2,2',4,4',5-pentaBDE on day 3 or 10 showed significantly impaired spontaneous motor behavior, whereas no effect was seen in mice exposed on day 19. Neonatal mice exposed to 2,2',4,4',5-penta[(14)C]BDE 99 on postnatal day 3, 10, or 19 were sacrificed 24 h or 7 days posttreatment. The amount of radioactivity, given as per mille ( per thousand) of total amount administered, was between 3.7 and 5.1 per thousand in the three different age categories at 24 h after administration. Seven days after the administration, 2,2',4,4',5-penta[(14)C]BDE or its metabolites could still be detected in the brain. The amount of radioactivity in the brain was not higher in mice exposed on day 3 or 10 when compared to exposure on day 19. Thus, the behavioral disturbances observed in adult mice following neonatal exposure to 2,2',4,4',5-pentaBDE are induced during a defined critical period of neonatal brain development.

Animals↗

Hierarchical approach to predicting permeation in ion channels.

A hierarchical computational strategy combining molecular modeling, electrostatics calculations, molecular dynamics, and Brownian dynamics simulations is developed and implemented to compute electrophysiologically measurable properties of the KcsA potassium channel. Models for a series of channels with different pore sizes are developed from the known x-ray structure, using insights into the gating conformational changes as suggested by a variety of published experiments. Information on the pH dependence of the channel gating is incorporated into the calculation of potential profiles for K(+) ions inside the channel, which are then combined with K(+) ion mobilities inside the channel, as computed by molecular dynamics simulations, to provide inputs into Brownian dynamics simulations for computing ion fluxes. The open model structure has a conductance of approximately 110 pS under symmetric 250 mM K(+) conditions, in reasonable agreement with experiments for the largest conducting substate. The dimensions of this channel are consistent with electrophysiologically determined size dependence of quaternary ammonium ion blocking from the intracellular end of this channel as well as with direct structural evidence that tetrabutylammonium ions can enter into the interior cavity of the channel. Realistic values of Ussing flux ratio exponents, distribution of ions within the channel, and shapes of the current-voltage and current-concentration curves are obtained. The Brownian dynamics calculations suggest passage of ions through the selectivity filter proceeds by a "knock-off" mechanism involving three ions, as has been previously inferred from functional and structural studies of barium ion blocking. These results suggest that the present calculations capture the essential nature of K(+) ion permeation in the KcsA channel and provide a proof-of-concept for the integrated microscopic/mesoscopic multitiered approach for predicting ion channel function from structure, which can be applied to other channel structures.

Bacterial Proteins↗

Molecular simulation of dioleoylphosphatidylcholine lipid bilayers at differing levels of hydration.

The structure and dynamics of the lipid and water components of dioleoylphosphatidylcholine bilayers at various levels of hydration were studied using molecular dynamics (MD) simulations. Equilibration of these systems proceeded by use of a hybrid MD and configurational-bias Monte Carlo technique using one atmosphere of pressure normal to the membrane and a set point for the lateral area derived from experimental Bragg spacings, combined with experimentally derived specific volumes for each of the system components. Membrane surface tensions were observed to be of the order of tens of dyn/cm. The transbilayer molecular fragment peak positions at low hydration were found to agree with experimental neutron and x-ray scattering profiles and previously published simulations. For hydration levels of 5.4, 11.4, and 16 waters/lipid, molecular fragment distributions and order parameters for the headgroup, lipid chains, and water were quantified. Spin-lattice relaxation rates and lateral self-diffusion coefficients of water agreed well with results from experimental nuclear magnetic resonance studies. Relaxation rates of the choline segments and chemical shift anisotropies for the phosphate and carbonyls were computed. Headgroup orientation, as measured by the P-N vector, showed enhanced alignment with the membrane surface at low hydration. The sign of the membrane dipole potential reversed at low hydration, with the membrane interior negative relative to the interlamellar region. Calculation of the number of water molecules in the headgroup hydration shell, as a function of hydration level, supports the hypothesis that the break point in the curve of Bragg spacing versus hydration level near 12 waters/lipid, observed experimentally by Hristova and White (1988. Biophys. J. 74:2419-2433), marks the completion of the first hydration shell.

Anisotropy↗

Combined Monte Carlo and molecular dynamics simulation of hydrated lipid-cholesterol lipid bilayers at low cholesterol concentration.

We have applied a hybrid equilibration and sampling procedure for the atomic level simulation of a hydrated lipid bilayer to systems consisting of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol, and palmitoyl-oleyl phosphatidylcholine (POPC) at low (approximately 6%) cholesterol concentration. The procedure is applied to bilayers of 94 molecules of DPPC, 6 molecules of cholesterol, and 3205 water molecules, and to bilayers of 120 molecules of POPC, 8 molecules of cholesterol, and 4268 water molecules, at a temperature of 325 K. After equilibration, three separate 400-ps continuous molecular dynamics runs, separated by 10,000 configurational bias Monte Carlo steps, were carried out for each system. Properties of the systems were calculated and averaged over the three separate runs. Results of the simulations are presented and compared with experimental data and with other recent simulations of DPPC and cholesterol, and of pure DPPC, and pure POPC. Certain properties of the bilayers are indistinguishable from cholesterol-free bilayers, including lateral diffusion and electron density. Other properties, most notably the order parameter profile, show the effect of cholesterol even at low concentrations.

1,2-Dipalmitoylphosphatidylcholine↗

Brominated flame retardants: a novel class of developmental neurotoxicants in our environment?

Brominated flame retardants are a novel group of global environmental contaminants. Within this group the polybrominated diphenyl ethers (PBDE) constitute one class of many that are found in electrical appliances, building materials, and textiles. PBDEs are persistent compounds that appear to have an environmental dispersion similar to that of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT). Levels of PBDEs are increasing in mother's milk while other organohalogens have decreased in concentration. We studied for developmental neurotoxic effects two polybrominated diphenyl ethers, 2,2',4,4'-tetrabromodiphenyl ether (PBDE 47) and 2,2',4,4',5-pentabromodiphenyl ether (PBDE 99)--congeners that dominate in environmental and human samples--together with another frequently used brominated flame retardant, tetrabromo-bis-phenol-A (TBBPA). The compounds were given to 10-day-old NMRI male mice, as follows: PBDE 47, 0.7 mg (1.4 micromol), 10.5 mg (21.1 micromol)/kg body weight (bw); PBDE 99, 0.8 mg (1.4 micromol), 12.0 mg (21.1 micromol)/kg bw; TBBPA, 0.75 mg (1.4 micromol), 11.5 mg (21.1 micromol)/kg bw. Mice serving as controls received 10 mL/kg bw of the 20% fat emulsion vehicle in the same manner. The present study has shown that neonatal exposure to PBDE 99 and PBDE 47 can cause permanent aberrations in spontaneous behavior, evident in 2- and 4-month-old animals. This effect together with the habituation capability was more pronounced with increasing age, and the changes were dose-response related. Furthermore, neonatal exposure to PBDE 99 also affected learning and memory functions in adult animals. These are developmental defects that have been detected previously in connection with PCBs.

Age Factors↗

Biochemical responses of fish sac fry and a primary cell culture of fish hepatocytes exposed to polychlorinated naphthalenes.

Chlorinated naphthalenes are planar halogenated aromatic compounds, which are widespread in the environment. Knowledge of their biochemical and toxicological actions in aquatic biota is, however, limited. The objective of this study was to assess the toxicity of highly chlorinated naphthalene congeners found in the aquatic environment on fish sac fry and to study their effects on xenobiotic metabolizing enzymes (CYP) using a short-term primary culture of fish hepatocytes and liver microsomes. A few days after hatching, rainbow trout sac fry were administered either Hallovax 1014, a mixture of 1,2,3,4,6,7-hexachloronaphthalene and 1,2,3,5,6, 7-hexachloronaphthalene (HxCN-mix), or 1,2,3,4,5,6, 7-heptachloronaphthalene (HpCN) (0.08, 0.8, and 4 microg/sac fry injected into the yolk sac). The exposure was terminated 2 weeks later. The naphthalene preparations did not cause any clinical signs of toxicity or difference in mortality rates between the control and treated groups. Immunohistochemical analysis of CYP1A expression in the treated sac fry revealed that staining was most pronounced in the hepatocytes and thereafter in kidney tubular epithelial cells. Moderate CYP1A staining was also seen in the mucosal epithelium of pyloric caecae and mild staining in the epithelium of olfactory organ. Staining in control sac fry was weak or absent. Exposure of the primary cell culture of trout hepatocytes to a low doses (</=10 ng/ml) of the chlorinated naphthalenes increased significantly CYP1A-associated EROD activity and CYP1A mRNA content, HxCN-mix being the most potent and thereafter HpCN and Hallovax 1014. The higher doses (50-100 ng/ml) of each naphthalene also inhibited EROD activity. However, the content of CYP1A mRNA or the intensity of the CYP1A protein band (58 kDa) recognized by anti-trout CYP1A peptide antibodies were not decreased with increasing polychlorinated naphthalene (PCN) concentration, indicating that the inhibition was not due to reduced protein synthesis. Furthermore, in vitro analyses of the inhibitory potential of PCNs on CYP1A activity with trout liver microsomes suggested that these naphthalene preparations may be CYP1A substrates and act as competitive inhibitors of CYP1A catalyst. Our results demonstrate that highly chlorinated naphthalenes are potent modulators of fish CYP1A enzyme and suggest that hepatocytes and tubular epithelial cells are the cell types that may be vulnerable to their metabolic products for cell injury in fish sac fry.

Animals↗

Clinical competence in pain assessment.

Our knowledge about the content of the clinical knowledge used by nurses in a surgical recovery unit for assessment of postoperative pain is fairly limited. The aim of the present study was to analyse and describe the variations of nurses' conceptions of the impact of clinical experience on competence in post-operative pain assessment. The informants consist of critical care nurses. A phenomenographical approach has been applied to tape-recorded interview data. The results reveal that clinical competence in pain assessment was described in three categories: (a) to be able to see; (b) to be able to differentiate; (c) to be able to give. The observations articulate what nurses perceive that they have learnt from experience in performing many clinical pain assessments and point to some difficulties in using a single-data source for the development of valid and truthful professional knowledge. In the development of professional experience, it is of the utmost importance to be able to change perspective from what is most frequent and general to what is special and unique, to base one's standpoint on the individual patient's experience and integrate this with previous professional experience.

Adult↗

Potent competitive interactions of some brominated flame retardants and related compounds with human transthyretin in vitro.

Brominated flame retardants such as polybrominated diphenyl ethers (PBDEs), pentabromophenol (PBP), and tetrabromobisphenol A (TBBPA) are produced in large quantities for use in electronic equipment, plastics, and building materials. Because these compounds have some structural resemblance to the thyroid hormone thyroxine (T(4)), it was suggested that they may interfere with thyroid hormone metabolism and transport, e.g., by competition with T(4) on transthyretin (TTR). In the present study, we investigated the possible interaction of several brominated flame retardants with T(4) binding to TTR in an in vitro competitive binding assay, using human TTR and 125 I-T(4) as the displaceable radioligand. Compounds were tested in at least eight different concentrations ranging from 1.95 to 500 nM. In addition, we investigated the structural requirements of these and related ligands for competitive binding to TTR. We were able to show very potent competition binding for TBBPA and PBP (10.6- and 7.1-fold stronger than the natural ligand T(4), respectively). PBDEs were able to compete with T(4)-TTR binding only after metabolic conversion by induced rat liver microsomes, suggesting an important role for hydroxylation. Brominated bisphenols with a high degree of bromination appeared to be more efficient competitors, whereas chlorinated bisphenols were less potent compared to their brominated analogues. These results indicate that brominated flame retardants, especially the brominated phenols and tetrabromobisphenol A, are very potent competitors for T(4) binding to human transthyretin in vitro and may have effects on thyroid hormone homeostasis in vivo comparable to the thyroid-disrupting effects of PCBs.

Animals↗

Combined Monte Carlo and molecular dynamics simulation of fully hydrated dioleyl and palmitoyl-oleyl phosphatidylcholine lipid bilayers.

We have applied a new equilibration procedure for the atomic level simulation of a hydrated lipid bilayer to hydrated bilayers of dioleyl-phosphatidylcholine (DOPC) and palmitoyl-oleyl phosphatidylcholine (POPC). The procedure consists of alternating molecular dynamics trajectory calculations in a constant surface tension and temperature ensemble with configurational bias Monte Carlo moves to different regions of the configuration space of the bilayer in a constant volume and temperature ensemble. The procedure is applied to bilayers of 128 molecules of POPC with 4628 water molecules, and 128 molecules of DOPC with 4825 water molecules. Progress toward equilibration is almost three times as fast in central processing unit (CPU) time compared with a purely molecular dynamics (MD) simulation. Equilibration is complete, as judged by the lack of energy drift in 200-ps runs of continuous MD. After the equilibrium state was reached, as determined by agreement between the simulation volume per lipid molecule with experiment, continuous MD was run in an ensemble in which the lateral area was restrained to fluctuate about a mean value and a pressure of 1 atm applied normal to the bilayer surface. Three separate continuous MD runs, 200 ps in duration each, separated by 10,000 CBMC steps, were carried out for each system. Properties of the systems were calculated and averaged over the three separate runs. Results of the simulations are presented and compared with experimental data and with other recent simulations of POPC and DOPC. Analysis of the hydration environment in the headgroups supports a mechanism by which unsaturation contributes to reduced transition temperatures. In this view, the relatively horizontal orientation of the unsaturated bond increases the area per lipid, resulting in increased water penetration between the headgroups. As a result the headgroup-headgroup interactions are attenuated and shielded, and this contributes to the lowered transition temperature.

Lipid Bilayers↗

Simulation study of a gramicidin/lipid bilayer system in excess water and lipid. I. Structure of the molecular complex.

This paper reports on a simulation of a gramicidin channel inserted into a fluid phase DMPC bilayer with 100 lipid molecules. Two lipid molecules per leaflet were removed to insert the gramicidin, so the resulting preparation had 96 lipid molecules and 3209 water molecules. Constant surface tension boundary conditions were employed. Like previous simulations with a lower lipid/gramicidin ratio (Woolf, T. B., and B. Roux. 1996. Proteins: Struct., Funct., Genet. 24:92-114), it is found that tryptophan-water hydrogen bonds are more common than tryptophan-phospholipid hydrogen bonds. However, one of the tryptophan NH groups entered into an unusually long-lived hydrogen bonding pattern with two glycerol oxygens of one of the phospholipid molecules. Comparisons were made between the behavior of the lipids adjacent to the channel with those farther away. It was found that hydrocarbon chains of lipids adjacent to the channel had higher-order parameters than those farther away. The thickness of the lipid bilayer immediately adjacent to the channel was greater than it was farther away. In general, the lipids adjacent to the membrane had similar orientations to those seen by Woolf and Roux, while those farther away had similar orientations to those pertaining before the insertion of the gramicidin. A corollary to this observation is that the thickness of the hydrocarbon region adjacent to the gramicidin was much thicker than what other studies have identified as the "hydrophobic length" of the gramicidin channel.

Biophysical Phenomena↗

Simulation study of a gramicidin/lipid bilayer system in excess water and lipid. II. Rates and mechanisms of water transport.

A gramicidin channel in a fluid phase DMPC bilayer with excess lipid and water has been simulated. By use of the formal correspondence between diffusion and random walk, a permeability for water through the channel was calculated, and was found to agree closely with the experimental results of Rosenberg and Finkelstein (Rosenberg, P.A., and A. Finkelstein. 1978. J. Gen. Physiol. 72:327-340; 341-350) for permeation of water through gramicidin in a phospholipid membrane. By using fluctuation analysis, components of resistance to permeation were computed for movement through the channel interior, for the transition step at the channel mouth where the water molecule solvation environment changes, and for the process of diffusion up to the channel mouth. The majority of the resistance to permeation appears to occur in the transition step at the channel mouth. A significant amount is also due to structurally based free energy barriers within the channel. Only small amounts are due to local friction within the channel or to diffusive resistance for approaching the channel mouth.

Biological Transport, Active↗

Flame retardant exposure: polybrominated diphenyl ethers in blood from Swedish workers.

Polybrominated diphenyl ethers (PBDEs) are used as additives in polymers and textiles to prohibit the development of fires. Because of the production and use of PBDEs, their lipophilic characteristics, and persistence, these compounds have become ubiquitous environmental contaminants. The aim of the present study was to determine potential exposures of PBDEs to clerks working full-time at computer screens and personnel at an electronics-dismantling plant, with hospital cleaners as a control group. Five PBDE congeners--2,2',4,4'-tetraBDE; 2,2',4,4',5,5'-hexaBDE; 2,2',4,4',5, 6'-hexaBDE; 2,2',3,4,4',5',6-heptaBDE; and decaBDE--were quantified in blood serum from all three categories of workers. Subjects working at the dismantling plant showed significantly higher levels of all PBDE congeners in their serum as compared to the control group. Decabromodiphenyl ether is present in concentrations of 5 pmol/g lipid weight (lw) in the personnel dismantling electronics; these concentrations are comparable to the concentrations of 2,2',4, 4'-tetraBDE. The latter compound was the dominating PBDE congener in the clerks and cleaners. The major compound in personnel at the dismantling plant was 2,2',3,4,4',5',6-heptaBDE. Concentrations of this PBDE congener are almost twice as high as for 2,2',4, 4'-tetraBDE in these workers and seventy times the level of this heptaBDE in cleaners. The total median PBDE concentrations in the serum from workers at the electronics-dismantling plant, clerks, and cleaners were 37, 7.3, and 5.4 pmol/g lw, respectively. The results show that decabromodiphenyl ether is bioavailable and that occupational exposure to PBDEs occurs at the electronics-dismantling plant.

Adult↗

Using theory and simulation to understand permeation and selectivity in ion channels.

It is clear that the function of ion channels must flow from their structure. With recent advances in computational power and methodology, it appears feasible to correlate structure to ion channel permeation at an atomistically detailed level of description. The overall strategy is to structure the calculations in a hierarchy, ranging from coarse-grained thermodynamic and kinetic descriptions to fine-grained molecular dynamics descriptions with atomic detail. Each level of description is connected to the others by appropriate statistical mechanical theory. The coarse-grained descriptions can be correlated directly with electrophysiological experiment. The fine-grained descriptions are used to parameterize the coarse-grained descriptions and to describe the permeation process at the most detailed level. This strategy has so far had varying degrees of success. It has successfully described water permeation through lipid bilayers and gramicidin channels. It has revealed the essential events of ion permeation through gramicidin channels at an atomistically detailed level. The role of channel protein motions in permeation has been elucidated. However, it appears that force fields used to describe molecular dynamics must be refined further to achieve completely accurate predictions of the permeation of such small ions as sodium. Channels with more complex structure and more multiion occupancy than gramicidin pose major computational challenges with respect to sampling protein conformations and ion distributions involved in the permeation process. Possible approaches to meeting these challenges are discussed.

Diffusion↗

Selectivity of electron-donor- and electron-acceptor-bonded silica packing materials for hydrophobic environmental contaminants in polar and non-polar eluents.

Electron-acceptor-bonded stationary phases, 2-(nitrophenyl)ethylsilyl (NPE) and 3-(p-nitrophenoxy)propylsilyl (NPO), and electron-donor-bonded phases, 3-(N-carbazolyl)propylsilyl (CZP), 2-(1-pyrenyl)ethylsilyl (PYE), and 5-coronenylpentylsilyl (COP), were prepared from silica particles and their selectivities were examined in both polar and non-polar solvents for specific isomers of polychlorodibenzo-p-dioxins (PCDDs), hexachloronaphthalenes (HxCNs) and planar and non-planar polychlorobiphenyl (PCB) congeners. Although no single stationary phase was able to separate all the isomer pairs that are coproduced during the synthesis of the PCDDs and HxCNs, pairs can be separated by selecting a suitable stationary phase and solvent. The separation of mixtures of PCDD isomers were found to be most successful with PYE and NPO phases, which yielded the opposite elution orders for each isomer pair that is produced as a mixture. Similar results were obtained for the HxCN isomers that were separated on PYE and CZP phases. The COP phase provided easier separation of non-ortho-substituted and mono-ortho-substituted PCBs from the other PCBs based on the planarity than PYE phase.

Chromatography, High Pressure Liquid↗

Distribution of Polychlorinated Naphthalene Congeners inEnvironmental and Source-Related Samples

Polychlorinated naphthalene (CN) congener profiles inenvironmental and source related samples were compared graphically and byprincipal component analysis. Samples investigated included biological,sediment, water, and air samples, technical polychlorinated biphenyl (PCB)and polychlorinated naphthalene (PCN) formulations, as well as municipalwaste incineration (MWI) fly ash and graphite electrode sludge. Biologicalsamples showed a preferential enrichment of planar, 1,3,5,7-substitutedtetra-, penta-, and hexachlorinated congeners and most of these samplesshowed profiles that displayed some similarity to those found in thetechnical PCB formulations. Sediment samples representing diffuse pollution,i.e., sediment samples from remote sites, showed an elevatedabundance of the planar hexa- and heptaCN congeners(1,2,3,4,6,7-/1,2,3,5,6,7- and 1,2,3,4,5,6,7-). The CN congener profile foundin these sediment samples and the two air samples were more similar to thetechnical PCB formulations than to the investigated MWI and graphite sludgesamples. Samples from three PCB contaminated lakes displayed similar congenerprofiles as Aroclor 1242, 1254 and Clophen A40. Two sediment samples and apike sample collected from the vicinity of a chloroalkali plant showedprofiles that were closely related to the investigated graphite electrodesludge sample. None of the environmental samples displayed profiles similarto low or medium chlorinated technical PCN (Halowax 1099, 1013, and 1014).

Journal Article↗

Computer simulation studies of biological membranes: progress, promise and pitfalls.

Because of the complexity of biological membranes, computer simulations are useful adjuncts to experimental work in their study. Simulations of model membranes have provided new insights. Progress in simulating more biologically realistic membranes will require further development of statistical mechanical theory applied specifically to these systems, in conjunction with the use of powerful computers.

Biochemistry↗