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6.8: Chemo-osmosis (an overview) - Biology

6.8: Chemo-osmosis (an overview) - Biology



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One of the most surprising discoveries in biology was the wide spread, almost universal use of H+ gradients to generate ATP. What was originally known as the chemiosmotic hypothesis was produced by the eccentric British scientist, Peter Mitchell (1920–1992)176. Before the significance of H+ membrane gradients was known, Mitchell proposed that energy captured through the absorption of light (by phototrophs) or the breakdown of molecules into more stable molecules (by various types of chemotrophs) relied on the same basic (homologous) mechanism, namely the generation of H+ gradients across membranes (the plasma membrane in prokaryotes or the internal membranes of mitochondria or chloroplasts (intracellular organelles, derived from bacteria – see below) in eukaryotes.

What makes us think that these processes might have a similar evolutionary root, that they are homologous? Basically, it is the observation that in both light- and chemical-based processes captured energy is transferred through the movement of electrons through a membrane-embedded “electron transport chain”. An electron transport chain involves a series of membrane and associated proteins and a series of reduction-oxidation or redox reactions (see below) during which electrons move from a high energy donor to a lower energy acceptor. Some of the energy difference between the two is used to move H+ ions across a membrane, generating a H+ concentration gradient. Subsequently the thermodynamically favorable movement of H+ down this concentration gradient (across the membrane) is used to drive ATP synthesis, a thermodynamically unfavorable process. ATP synthesis itself involves the rotating ATP synthase. The reaction can be written:

[H^+_{outside} + ADP + P_i ⇌ ATP + H_2O + H^+_{inside}]

where “inside” and “outside” refer to compartments defined by the membrane containing the electron transport chain and the ATP synthase. Again, this reaction can run backwards. When this occurs, the ATP synthase acts as an ATPase (ATP hydrolase) that can pump H+ (or other molecules) against its concentration gradient. Such pumping ATPases establishes most biologically important molecular gradients across membranes. In such a reaction:

ATP + H2O + molecule in low concentration region ⇌ ADP + Pi + molecule in low concentration region.

The most important difference between phototrophs and chemotrophs is how high energy electrons enter the electron transport chain.


Inhibitors of HSP90 in melanoma

HSP90 (heat shock protein 90) is an ATP-dependent molecular chaperone involved in a proper folding and maturation of hundreds of proteins. HSP90 is abundantly expressed in cancer, including melanoma. HSP90 client proteins are the key oncoproteins of several signaling pathways controlling melanoma development, progression and response to therapy. A number of natural and synthetic compounds of different chemical structures and binding sites within HSP90 have been identified as selective HSP90 inhibitors. The majority of HSP90-targeting agents affect N-terminal ATPase activity of HSP90. In contrast to N-terminal inhibitors, agents interacting with the middle and C-terminal domains of HSP90 do not induce HSP70-dependent cytoprotective response. Several inhibitors of HSP90 were tested against melanoma in pre-clinical studies and clinical trials, providing evidence that these agents can be considered either as single or complementary therapeutic strategy. This review summarizes current knowledge on the role of HSP90 protein in cancer with focus on melanoma, and provides an overview of structurally different HSP90 inhibitors that are considered as potential therapeutics for melanoma treatment.

Keywords: Apoptosis Chaperone HSP70 HSP90 inhibitors Melanoma Targeted therapy.

Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Schematic representation of HSP90 protein…

Schematic representation of HSP90 protein domain structure. Functions of each domain and HSP90-interacting…

Exemplary chaperone cycle of HSP90.…

Exemplary chaperone cycle of HSP90. The consecutive steps are marked with numbers. Unfolded…

Major melanoma-associated signaling pathways, and…

Major melanoma-associated signaling pathways, and their roles in melanoma. Proteins identified as direct…

HSP90 inhibitors exerting anti-melanoma activity.…

HSP90 inhibitors exerting anti-melanoma activity. Compounds were classified based on their binding sites…


&alpha2-3,6,8,9 Neuraminidase A

&alpha2-3,6,8,9 Neuraminidase A is a broad specificity sialidase, which cleaves linear and branched non-reducing terminal sialic acid residues from glycoproteins, glycopeptides, and oligosaccharides. It can be used for glycan analysis and characterization and intact glycoprotein remodeling, in vitro and in vivo.

  • Recombinant enzyme with no detectable endoglycosidase or other exoglycosidases contaminating activities
  • Acts on both Neu5Ac and Neu5Gc
  • Double digest with other exoglycosidases and endoglycosidases
  • Tolerant of moderate levels (0.5-1.0%) of detergents
  • &ge95% purity, as determined by SDS-PAGE and intact ESI-MS
  • Optimal activity and stability for up to 24 months

Neuraminidase is the common name for Acetyl-neuraminyl hydrolase (Sialidase). &alpha2-3,6,8,9 Neuraminidase A catalyzes the hydrolysis of all linear and branched non-reducing terminal sialic acid residues from glycoproteins and oligosaccharides. The enzyme releases &alpha2-3 and &alpha2-6 linkages at a slightly higher rate than &alpha2-8 and &alpha2-9 linkages.

Specificity


Detailed Specificity
&alpha2-3,6,8,9 Neuraminidase A will cleave branched sialic acid residues that are linked to an internal residue. This oligosaccharide from fetuin is an example of a side-branch sialic acid residue that can efficiently be cleaved (1).


Product Source

Reagents Supplied

The following reagents are supplied with this product:

&alpha2-3,6,8,9 Neuraminidase A P0722SVIAL -20 1 x 0.04 ml 20,000 units/ml
GlycoBuffer 1 B1727SVIAL -20 1 x 1 ml 10 X
&alpha2-3,6,8,9 Neuraminidase A P0722LVIAL -20 1 x 0.2 ml 20,000 units/ml
GlycoBuffer 1 B1727SVIAL -20 1 x 1 ml 10 X

Unit Definition

One unit is defined as the amount of enzyme required to cleave > 95% of the terminal &alpha-Neu5Ac from 1 nmol Neu5Ac&alpha2-3Gal&beta1- 3GlcNAc&beta1-3Gal&beta1-4Glc-AMC, in 1 hour at 37°C in a total reaction volume of 10 &mul.

Unit Definition Assay
Two fold dilutions of &alpha2- 3,6,8,9 Neuraminidase A are incubated with 1 nmol AMC-labeled substrate and 1X GlycoBuffer 1 in a 10 &mul reaction. The reaction mix is incubated at 37°C for 1 hour. Separation of reaction products are visualized via thin layer chromatography (3).

Reaction Conditions

1X GlycoBuffer 1
5 mM CaCl2
50 mM sodium acetate
(pH 5.5 @ 25°C)

Storage Buffer

50 mM NaCl
20 mM Tris-HCl
1 mM EDTA
pH 7.5 @ 25°C

Heat Inactivation

Molecular Weight

Specific Activity

Companion Products

  1. Reactions may be scaled-up linearly to accommodate larger reaction volumes.
  2. The amount of exoglycosidase enzyme required varies when different substrates are used. Start with 1&ndash2 &mul for 1 &mug of glycoprotein or 100 nM of oligosaccharide for one hour in a 10&ndash25 &mul reaction. If there is still undigested material, let the reaction go overnight.
  3. Higher concentrations of enzyme as well as longer incubation times may be necessary for cleavage of branched structures.
  1. Iwamori, M., Ohta, Y., Uchida, Y. and Tsukada, Y. (1997). Glycocon. J. 1, 67-73.
  2. McLeod, E. New England Biolabs, Inc. Unpublished observation
  3. Wong-Madden, S. T. and Landry, D. (1995). Glycobiology. 5, 19-28.
  1. What is the difference between the four Neuraminidase enzymes sold by NEB: &alpha2-3,6,8 Neuraminidase, &alpha2-3,6,8,9 Neuraminidase A, &alpha2-3 Neuraminidase and &alpha2-3 Neuraminidase S?
  2. What is a good positive control for &alpha2-3,6,8,9 Neuraminidase A?
  3. Can I use &alpha2-3,6,8,9 Neuraminidase A in a double digest with other exoglycosidases and/or endoglycosidases?
  4. Can I use &alpha2-3,6,8,9 Neuraminidase A in a double digest with Endo H/Hf, O-Glycosidase or PNGase F?
  5. Does this enzyme require denaturing conditions to act on glycoproteins?
  6. What is a good method to re-purify a glycan or glycopeptide after exoglycosidase treatment?
  7. Do detergents inhibit glycosidases?
  8. What are glycosidases and their uses?
  9. Do the NEB Neuraminidase enzymes cleave both N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) residues?
  10. Is it necessary to treat my glycoprotein concomitantly with Neuraminidase and O-Glycosidase?
  11. How much exoglycosidase should be used?
  • Don&rsquot forget to include Neuraminidase in a digestion with O-Glycosidase.
  • f you are trying to cleave an oligosaccharide with a branched sialic acid residue you will want to use &alpha2-3,6,8,9 Neuraminidase A

Product Citation Tool

  • Albrecht, S., Vainauskas, S., Stöckmann, H., McManus, C., Taron, C.H. and Rudd, P.M. (2016) . Comprehensive Profiling of Glycosphingolipid Glycans Using a Novel Broad Specificity Endoglycoceramidase in a High-Throughput Workflow.. May 388(9), 4795-802. Anal Chem.. PubMedID: 27033327

Specifications

  • P0722S_L_v1_0021602
  • P0722S_L_v1_0011605
  • P0722S_L_v1_0021608
  • P0722S_L_v1_0021612
  • P0722S_L_v1_0021706
  • P0722S_L_v1_0021710
  • P0722S_L_v1_0021801
  • P0722S_L_v1_0021803
  • P0722L_v1_10020203
  • P0722S_v1_10020388
  • P0722S_v1_10022690
  • P0722L_v1_10028396
  • P0722S_v1_10031676
  • P0722L_v1_10040007
  • P0722S_v1_10040005
  • P0722S_v1_10057252
  • P0722L_v0_10057251
  • P0722L_v1_10064911
  • P0722S_v1_10064910
  • P0722L_v1_10070591
  • P0722S_v1_10075161
  • P0722S_v1_10079100
  • P0722L_v1_10084288
  • P0722S_v1_10084289
  • P0722L_v1_10091048
  • P0722S_v1_10110147
  • P0722S_v1_10110741

This product is covered by one or more patents, trademarks and/or copyrights owned or controlled by New England Biolabs, Inc (NEB).

While NEB develops and validates its products for various applications, the use of this product may require the buyer to obtain additional third party intellectual property rights for certain applications.

For more information about commercial rights, please contact NEB's Global Business Development team at [email protected]

This product is intended for research purposes only. This product is not intended to be used for therapeutic or diagnostic purposes in humans or animals.

New England Biolabs (NEB) is committed to practicing ethical science &ndash we believe it is our job as researchers to ask the important questions that when answered will help preserve our quality of life and the world that we live in. However, this research should always be done in safe and ethical manner. Learn more.


Glasgow Coma Scale Interpretation

Glasgow Coma Scale interpretation is not as simple as it might seem. Even medically-trained personnel have problems judging whether a patient is conscious or unconscious. Modern medicine also means that many trauma victims are intubated on-scene it is impossible to measure awareness and arousal at this point. Even the administration of pain medication will affect results.

Patients who have been intubated on-scene will have an artificial Glasgow Coma Scale result and are usually assessed using the Full Outline of UnResponsiveness (FOUR) score.

Many variables make it difficult to observe the correct level of response. Facial trauma may make assessing eye movement difficult. A foreign victim might not speak the language of the emergency team and be unable to follow commands. A victim may be deaf. Alcohol and drug use can affect all three response parameters. Spinal cord damage will make motor responses and movements in reaction to pain unreliable.

The Glasgow Coma Scale range of scores is not just the sum of all three tests it measures arousal, verbally-assessed awareness, and motor-assessed awareness separately. The total Glasgow Coma Scale score is a rapid way to determine victim response in an emergency but the separate parts are more important during longer-term care.

This means that score expression should be noted both as a total and per element, for example, GCS11 = E5V2M4.

A Glasgow Coma Scale 7 result would similarly be split into its elements. This is important for medical staff as GCS7 = E1V3M4 and GCS7 = E2V1M4 could indicate different treatments or diagnoses.

It is impossible to score 0 Glasgow Coma Scale 3 is the lowest possible outcome. Glasgow Coma Scale 15 is the highest possible score.


Where are chylomicrons synthesized?

Chylomicrons synthesize in the cells of the intestinal wall from where they pass into the blood plasma. Its composition is 86–94% triglycerides, 3–8% phospholipids, 0.5–1% cholesterol, and 2% special proteins called apolipoproteins. The total lipid content is 98-99%. It has the lowest density.

Chylomicrons synthesize

What is the function and catabolism of chylomicrons?

The function of Chylomicron is to transports exogenous lipids to the liver, fat, heart, and skeletal muscle tissue. At these locations, the activity of lipoprotein lipase lowers triglycerides. When most of the core of triacylglycerol has been hydrolyzed, its residues form and transfer to the liver.

The catabolism of these lipoproteins is very similar, although they synthesize in response to different conditions as follow:

  • In the light of a blood vessel, lipoproteins “collide” with HDL, which transfers apoCII and apoE to them, becoming “mature particles”.In this case, the resulting fatty acids penetrate the tissue ( adipose tissue, muscles, and others), and the Apoc-II lipoprotein lipase activator again goes to HDL.
  • The particle size of the chylomicron decreases and it turns into a residue.
  • Its residue rapidly absorbs by the liver due to receptor binding of the endothelium with apoE and subsequent endocytosis, where it finally degrades.
  • Thus, it provides the transfer of food lipids from the intestine to the liver.

Let’s dive bit more into detail about it.

What are immature, mature, and remnant types of chylo microns?

Immature chylomicron makes up of absorbing cells in the small intestine known as enterocytes. These are relatively large with diameters of 75 to 1,200 nanometers. It composed mainly of triglycerides (85%), cholesterol, and cholesterol ester. The main apolipoprotein component is apolipoprotein-48 B.

In the case of mature chylomicrons, these are circulating in lymph and blood, chylomicron exchanges components with high-density lipoprotein (HDL). HDL is apolipoprotein-II C and apolipoprotein E provides the initial chylomicrons, to convert into mature chylomicrons. APOC2 is a cofactor for lipoprotein lipase (LPL) activity.

Chylomicron Remnant: When the triglyceride reserve consumes (distributed), it converts APOC2 back to HDL (which APOE retains), leaving chylomicrons remnants of only 20-50 nm. APOB48 and APOE are important for the identification of chylomicron remnants in the liver due to endocytosis and degradation.

Let’s compare Chylomicrons with other terms.

Chylomicron vs VLDL

The chylomicrons are large lipoproteins with an extremely low density that transport dietary lipids from intestine to tissues while the VLDL, very low-density lipoproteins, synthesized in the liver and transport lipids to tissues.VLDL lose triacylglycerols and some apoproteins and phospholipids in the body.

Chylo-micron and Micelles

Micelles are aggregates of several molecules. This is in the form in which fatty acids, glycerides, sterols absorb into the intestinal cells. They made of phospholipids while Chylomicrons a type of lipoproteins that carry dietary cholesterol and triglycerides from the small intestine out to the body tissues.

Chylo-micron test

The so-called refrigerator test is a qualitative detection method for chylomicrons. In the process, fasting blood serum store overnight at 4 ° C. If a “cream layer” creates at the top, this consider positive evidence of chylomicrons. While homogeneous turbidity indicates an increased concentration of VLDL.


Characterization and Discrimination of the ALPs

Many different biochemical and immunological methods have been used to discriminate between and selectively assay the different ALPS at the enzyme and protein level. Three general methods have proved particularly useful: thermostability studies differential inhibition with various aminoacids, small peptides and other low molecular weight substances and immunologic methods [39].

Thermostability

The intestinal and L/B/K ALPs are rapidly inactivated at temperature 㹥 ଌ (Table  2 ). In contrast, placental and placental-like ALPS are remarkably thermostable. They may be heated at 65 ଌ for an hour or more without loss of activity. However, the intestinal ALP is somewhat more thermostable than the L/B/K ALP. It has also been shown that in serum, liver ALP is slightly, though significantly, more thermostable than bone ALP [39].

Tableਂ

Relative thermostabilities of human ALPs [39]

Time in minute required to give 50 % inactivation of different human ALPs at 56 ଌ and 65 ଌ

Inhibition Studies

Various low molecular weight substances show differential inhibition of the different ALPs. Table  3 summaries the effects with five inhibitors which have been extensively used. The L/B/K ALPs are more sensitive to inhibition with l -homoarginine (Har) than placental, placental-like or intestinal ALPs. In contrast, placental, placental-like and intestinal ALPS are about 30 times more sensitive to inhibition with l -phenylalanine (Phe) than the L/B/K ALPs. r,-Phenylalanyl-glycyl-glycine (Pgg) gives sharp differential inhibition between placental, intestinal and L/B/K ALPs. It also differentiates between placental ALP and placental-like ALP, which with this inhibitor more nearly resembles intestinal ALP. l -Leucine (Leu) characteristically gives much stronger inhibition with placental-like ALP than with the other ALPs. Levamisole (Leva) is a particularly potent inhibitor of L/B/K ALP, but has little inhibitory effect on the other ALPs [39].

Tableਃ

Effects of various inhibitors on different Huaman ALPs [19]

InhibitorsALP
L/B/K ALPIntestinalPlacentalPlac-like
l -Plenylalanine (Phe)310.81.10.8
l -Homoarginine (Har)2.74036
l -Phenylalanineglycylglycine (Pgg)30.63.70.12.9
l -Leucine (Leu)13.13.65.70.6
Levamisole (Leva)0.036.81.72.7

Concentrations (nmol/l) of various inhibitors required to produce 50 % inhibition of different human ALPs under standardized conditions

Immunologic Studies

Antisera raised in rabbits against purified placental ALP cross-react with placental- like ALP and intestinal ALP, but not with L/B/K ALP. Complementary results are obtained with antisera raised against intestinal ALP or L/B/K ALP. These findings demonstrate that some, though not all, of the antigenic determinants detected on placental ALPਊre also present on intestinal ALP, but the placental and placental like ALPs are immunologically very similar. Some but not other monoclonals, raised against placental and intestinal ALPs react with both ALPs and some, though not other, monoclonals differentiate the placental and placental-like ALP. Combinations of these various biochemical and immunological techniques have been used to devise methods which give precise analytical information about the quantities of each of the ALPs when they are present together in a tissue extract or body fluid such as serum or amniotic fluid.

l -Phenylalanyl-glycyl-glycine (Pgg) gives sharp differential inhibition between placental, intestinal and L/B/K ALPs. Leva is particularlyਊ potent inhibitor of L/B/K ALP, but has little inhibitory effect on other ALPs. It should be noted that these various inhibitors are stereospecific and uncompetitive [19].


&alpha2-3,6,8 Neuraminidase

&alpha2-3,6,8 Neuraminidase catalyzes the hydrolysis of &alpha2-3, &alpha2-6, and &alpha2-8 linked sialic acid residues from glycoproteins and oligosaccharides.

  • Recombinant enzyme with no detectable endoglycosidase or other exoglycosidases contaminating activities
  • Acts on both Neu5Ac and Neu5Gc
  • Fast digestion, removal of sialic acids in 5 minutes

Neuraminidase is the common name for Acetyl-neuraminyl hydrolase (Sialidase). This Neuraminidase catalyzes the hydrolysis of &alpha2-3, &alpha2-6, and &alpha2-8 linked N-acetylneuraminic acid residues from glycoproteins and oligosaccharides.

Substrate Specificity:

Product Source

Reagents Supplied

The following reagents are supplied with this product:

&alpha2-3,6,8 Neuraminidase P0720SVIAL -20 1 x 0.04 ml 50,000 units/ml
GlycoBuffer 1 B1727SVIAL -20 1 x 1 ml 10 X

Unit Definition

One unit is defined as the amount of enzyme required to cleave > 95% of the terminal &alpha-Neu5Ac from 1 nmol Neu5Ac&alpha2-3Gal&beta1-3GlcNAc&beta1-3Gal&beta1-4Glc-7-amino-4-methyl-coumarin (AMC), in 5 minutes at 37°C in a total reaction volume of 10 µl.

Two fold dilutions of &alpha2-3,6,8 Neuraminidase are incubated with 1 nmol AMC-labeled substrate and 1X GlycoBuffer 1 in a 10 µl reaction. The reaction mix is incubated at 37°C for 5 minutes. Separation of reaction products are visualized via thin layer chromatography (3).

Reaction Conditions

1X GlycoBuffer 1
Incubate at 37°C

1X GlycoBuffer 1
5 mM CaCl2
50 mM sodium acetate
(pH 5.5 @ 25°C)

Storage Buffer

50 mM NaCl
20 mM Tris-HCl
5 mM EDTA
pH 7.5 @ 25°C

Heat Inactivation

Molecular Weight

Companion Products

  1. Roggentin, P. et al. (1988). FEBS Lett. 238(1), 31-34.
  2. Guan, C., New England Biolabs unpublished observations.
  3. Wong-Madden, S.T. and Landry, D. (1995). Glycobiology. 5, 19-28.
  • P0720Datasheet-Lot0131205
  • P0720Datasheet-Lot0141206
  • P0720Datasheet-Lot0141210
  • P0720Datasheet-Lot0151302
  • P0720Datasheet-Lot0141303
  • P0720Datasheet-Lot0151305
  • P0720Datasheet-Lot0151310
  • P0720Datasheet-Lot0151312
  • P0720Datasheet-Lot0151407
  • P0720Datasheet-Lot0151408
  • P0720Datasheet-Lot0171412
  • P0720Datasheet-Lot0151501
  • P0720Datasheet-Lot0151504

Product Citation Tool

Specifications

  • P0720S_L_v1_0161603
  • P0720S_L_v1_0171609
  • P0720S_L_v1_0171612
  • P0720S_L_v1_0191704
  • P0720S_L_v1_0191707
  • P0720S_L_v1_0201710
  • P0720S_L_v1_0201801
  • P0720L_v1_10010266
  • P0720L_v1_10015145
  • P0720S_v1_10018751
  • P0720S_v1_10026475
  • P0720L_v1_10026474
  • P0720S_v1_10031657
  • P0720L_v1_10044263
  • P0720S_v1_10044262
  • P0720S_v1_10044661
  • P0720L_v1_10054879
  • P0720L_v1_10056317
  • P0720L_v1_10061039
  • P0720S_v1_10062665
  • P0720L_v1_10065575
  • P0720S_v1_10065577
  • P0720L_v1_10075882
  • P0720S_v1_10102998
  • P0720S_v1_10113722
  • P0720Datasheet-Lot0131205
  • P0720Datasheet-Lot0141206
  • P0720Datasheet-Lot0141210
  • P0720Datasheet-Lot0151302
  • P0720Datasheet-Lot0141303
  • P0720Datasheet-Lot0151305
  • P0720Datasheet-Lot0151310
  • P0720Datasheet-Lot0151312
  • P0720Datasheet-Lot0151407
  • P0720Datasheet-Lot0151408
  • P0720Datasheet-Lot0171412
  • P0720Datasheet-Lot0151501
  • P0720Datasheet-Lot0151504

This product is covered by one or more patents, trademarks and/or copyrights owned or controlled by New England Biolabs, Inc (NEB).

While NEB develops and validates its products for various applications, the use of this product may require the buyer to obtain additional third party intellectual property rights for certain applications.

For more information about commercial rights, please contact NEB's Global Business Development team at [email protected]

This product is intended for research purposes only. This product is not intended to be used for therapeutic or diagnostic purposes in humans or animals.

New England Biolabs (NEB) is committed to practicing ethical science &ndash we believe it is our job as researchers to ask the important questions that when answered will help preserve our quality of life and the world that we live in. However, this research should always be done in safe and ethical manner. Learn more.


Microalgal Nutraceuticals

3.4 Chlorella: The Green Nutraceutical

The green cellular microalga Chlorella is widely sold as a health food, food supplement, and nutraceutical ( Morita, 1999 ). In the Far East, Chlorella has been used as an alternative medicine since ancient times. In China and the Orient, this Chlorophyte is considered as a traditional food similar to a nutraceutical. Nowadays, the microalgae Chlorella is produced and marketed as a health food supplement in many countries, like China, Japan, Europe, and the United States. Its estimated total production is around 2000 tons/year ( Batista et al., 2013 ) of dried Chlorella in the United States, Japan, China, Taiwan, and Indonesia. Because of its content of nutrients and positive health effects, Chlorella is considered an important functional food and nutraceutical. Concerning its composition, Chlorella is composed of 55–60% protein, 1–4% chlorophyll, 9–18% dietary fiber, and numerous minerals and vitamins ( Shim et al., 2008 ). Reports on the protein of Chlorella reveal all essential amino acids required for the nutrition of heterotrophic organisms. The detoxication of metals and pesticides performed by Chlorella is associated with porphyrin rings in chlorophyll or glutathione-induced pathway production by vitamin B12. Chlorella also accumulates large amounts of lutein, which has been associated with prevention and treatment of macular degeneration ( Shibata et al., 2003 ). This Chlorophyte is also able to lower cholesterol levels and decrease blood pressure. The consumption of Chlorella significantly decreased the low-density lipoprotein and the cholesterol levels. As in the case of other microalgae, Chlorella consumption as a nutraceutical product could exhibit side effects ( Gouveia et al., 2007 ). Among the registered effects, each commercial brand could exert different response among consumers, as cases of gastrointestinal diseases, nausea, and vomiting. This Chlorophyte has been classified as a weak allergen. Figure 3 shows the different pigments contained in the diverse microalgal nutraceuticals.

Figure 3 . The main pigments contained in microalgae used as Nutraceuticals.


New Jersey Department of Education

The goal of science education curriculum is to produce students who have gained sufficient knowledge of the practices, crosscutting concepts, and core ideas of science and engineering to engage in public discussions on science-related issues, to be critical consumers of scientific information related to their everyday lives, and to continue to learn about science throughout their lives. They should come to appreciate that science and the current scientific understanding of the world are the result of many hundreds of years of creative human endeavor. It is especially important to note that the above goals are for all students, not just those who pursue careers in science, engineering, or technology or those who continue on to higher education (p. 9, NRC, 2012).
Given this goal, an integrated science curriculum model should drive the formation of middle school science curriculum because:

  • The nature of science is complex and multidisciplinary.
  • Learning theory research in science shows expert knowledge base develops better through interdisciplinary connections and not through isolated content.
  • Effective research-based practices for curriculum and instruction in science and engineering are supported through this approach.

Nature of Science

The nature of science is complex and multidisciplinary. From research about how scientists work, we know that scientists do not work in isolation in their own house of physics, or biology or chemistry but they reach out and create networks of scientists within and across disciplines who can contribute understanding, share ideas, and critique evidence and explanations. As we see in the science of global climate change, scientists work across the fields of geology, physics, and biology to provide evidence, plan investigations, and develop models to represent new ways to think about Earth systems. Important practices like engaging in argument from evidence, modeling, and communicating information do not occur in isolation but rely on feedback from within and across scientific communities and disciplines. Basing the middle school model curriculum in an integrated model where the students are engaged with a variety of topics at each grade, focused on the connection of ideas across the domains, enhances the interdisciplinary nature of science.

Learning Theory

In the elementary years, students build their understandings of core concepts across all three domains of science: physical, life and Earth and space. Continuing this model in grades 6-8 better supports student learning in that there will not be a large gap of time in which a student does not engage in a specific discipline. This model takes advantage of current research which recognizes that there is variation across children at a given age and that thinking does not develop along a preset roadmap for each student. It allows middle school students to build on what they know and think they understand from their elementary years with the goal in middle school of helping students to revise their knowledge and understanding about those core ideas. Learning theory research shows expert knowledge base develops better through interdisciplinary real-world connections then through isolated content. This is especially important in middle school where motivation is critical to learning. An integrated and better articulated middle school model science curriculum that reflects what we know currently about how children learn science and how their mastery develops over time promotes deeper learning in science. As we know and understand about how students develop understanding while learning content, it informs teachers' practice if teachers understand where their students are in their understanding of core ideas, and anticipate what students' misconceptions and struggles may be, they are better able to differentiate instruction and provide scaffolding that allows students to develop an integrated and deeper understanding of the science.

Research Based Science Instruction and Curriculum

Effective science instruction can take many forms but includes similar components. According to the Center on Instruction's 2010 report, Effective Science Instruction: What does the Research Tell Us?, research-based effective practices of curriculum and instruction important to science learning are: Motivation, Eliciting Students' Prior Knowledge, Intellectual Engagement Use of Evidence to Critique Claims, and Sense-Making. The integrated model may be better able to support some of these instructional practices especially if it frames curriculum around engaging, relevant, and real-world interdisciplinary questions that will increase student motivation, intellectual engagement and sense-making. Effective science instruction helps middle school students build their understandings and practices, makes connections among and between core concepts and practices, and links to their prior knowledge. Students in grades 6-8 come to understand the natural world in a more scientifically accurate way and understand the nature of science.

Science curriculum should be thematic with a focus on connections among and between core concepts and practices. This approach reinforces the interdisciplinary nature of science and allows for a sequential progression of skills and concepts. This supports developmentally appropriate teaching and assessments. Each grade level has its own specific standards from each science domain that are seen as stepping stones in the progression of learning about a core idea and that meet a specific level of understanding. The idea is to embed technology and engineering in this interdisciplinary progression which would also be coordinated with the Common Core State Standards.
The model science curriculum for grades K-8 provides a common pathway that mitigates some of the challenges a student experiences when they transfer between schools or districts in the state. The model also allows educators from multiple districts in a region to align teaching and learning assessments and professional development. Districts retain their local control over the implementation of a common curriculum. The day to day decisions about how best to meet the specific needs of a student still rest with the local teacher of science and school. The common model for local curriculum development allows school districts to share science curriculum resources, formative and summative assessment items, teacher professional development, and other tools.


Biotin and the biotin-binding proteins

Biotin

Biotin is a vitamin (Vitamin H, Vitamin B7, Coenzyme R) that is present in small amounts in all living cells and is critical for a number of biological processes including cell growth and the citric acid cycle. Biotin is abundant in certain plant and animal tissues such as corn kernels, egg yolk, brain, liver and blood. The valeric acid side chain of the biotin molecule can be derivatized in order to incorporate various reactive groups that facilitate the addition of a biotin tag to other molecules. Because biotin is relatively small (244.3 Daltons), it can be conjugated to many proteins and other molecules without significantly altering their biological activity. The highly specific interaction of biotin-binding proteins with biotin makes it a useful tool in assay systems designed to detect and target biological analytes.

Chemical structure of biotin. Biotin, also known as B-vitamin B7 (formerly vitamin H and coenzyme R) is water soluble. The molecule is comprised of an ureido ring joined with a tetrahydrothiophene ring. Biotin is a coenzyme for carboxylase enzymes and biotin is required for the synthesis of these molecules: fatty acids, isoleucine, and valine. Biotin is also involved in gluconeogenesis.

Once biotin is attached to a molecule, the biotin tag can be used to facilitate affinity purification of that molecule using an immobilized biotin-binding protein. Alternatively, a biotinylated molecule can be immobilized through interaction with a biotin-binding protein, and then used to affinity purify other molecules that specifically interact with it (i.e., co-immunoprecipitation or pull-down assays). In the context of immunohistochemistry and immunoblotting, biotin is most often conjugated to primary or secondary antibodies, and the biotin tag is then detected with a biotin-binding protein that is conjugated to an enzyme, fluorophore or other reporter molecule. Many proteins, such as antibodies, can be labeled with several biotin tags, each able to be bound by a biotin-binding protein. An optimized biotin-to-probe ratio can greatly increase the signal output of a detection system making it possible to create very sensitive assays.

Biotin-labeled antibodies and other molecules are readily available from commercial suppliers making assay development routine for many applications. For assays in which a biotinylated probe is not available, there are many biotinylation reagents that enable researchers to chemically label proteins, nucleic acids and surface materials to make custom assay reagents.


Watch the video: KS3 Osmosis (August 2022).