Thermo Fisher Scientific

Phosphate Buffered Saline (PBS)1

Definition:

Phosphate buffered saline (PBS) is a sterile, aqueous solution containing salts that mimic the ionic composition of human extracellular fluids.It is commonly used in cell biology, microbiology, and biochemistry research.12345

Composition:123

PBS typically contains the following salts:Sodium chloride (NaCl), Potassium chloride (KCl), Sodium phosphate dibasic (Na2HPO4), and Potassium phosphate monobasic (KH2PO4).123456

Properties:1

• Isotonic: Has the same osmotic pressure as human blood, preventing cells from shrinking or swelling.12
• Non-toxic: Safe for use with most cell types.
• pH 7.2-7.4: Slightly alkaline, providing a stable environment for cells.
• Buffering capacity: Resists changes in pH, making it suitable for cell culture and other experiments where pH control is important.

Uses:

PBS is widely used in various research applications, including:

• Cell washing and rinsing
• Diluting cell suspensions
• Transporting and storing cells
• Preparing cell culture media
• Maintaining osmotic balance in assays
• Dissociation of cells

Preparation:

PBS can be prepared in the laboratory by dissolving the required salts in distilled water.Commercial solutions are also readily available.

Types:

• Standard PBS: Contains all the salts listed above.
• DPBS (Dulbecco's Phosphate Buffered Saline): Similar to standard PBS, but also contains calcium and magnesium ions.

Storage:

PBS can be stored at room temperature or in the refrigerator (2-8°C).It is typically sterile and should be discarded if it becomes cloudy or contaminated.

Additional Notes:

• PBS is available in various concentrations, such as 1x and 10x.
• Different formulations of PBS may exist, depending on the specific application.
• PBS is a common reagent in cell biology and can be purchased from various scientific suppliers.

The Endoplasmic Reticulum (ER) is a vast network of membranes in eukaryotic cells, crucial for protein synthesis, lipid production, and transporting molecules, acting as a cellular manufacturing and transport system connected to the nuclear envelope . It has two main types: Rough ER , studded with ribosomes for protein processing, and Smooth ER , involved in lipid synthesis, detoxification, and calcium storage.12345

Structure & Types

• Network: A continuous membrane system of flattened sacs (cisternae) and tubules extending throughout the cytoplasm.
• Rough ER (RER): Has ribosomes on its surface, making proteins for secretion or insertion into membranes.
• Smooth ER (SER): Lacks ribosomes; synthesizes lipids, metabolizes carbohydrates, and detoxifies.
• Continuity: The ER membrane connects directly to the outer membrane of the nucleus.123456

Key Functions

• Protein Synthesis & Folding: RER makes and folds proteins, adding carbohydrates (glycosylation) and forming disulfide bonds.
• Lipid Synthesis: SER produces lipids, fats, and steroids, vital for cell membranes and hormones.
• Transport: Acts as a highway, moving proteins, lipids, and other molecules within the cell.
• Calcium Storage: Regulates intracellular calcium levels, crucial for cell signaling.
• Detoxification: SER detoxifies drugs and metabolic waste.12345

Parts & Components

• Lumen: The internal space within the ER.
• Cisternae: Flattened, sac-like structures.
• Tubules: Branching, tube-like structures.
• Ribosomes: Attached to RER, responsible for protein synthesis.1234

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The nucleus (plural: nuclei) is the command center of a eukaryotic cell, housing the cell's DNA (chromosomes) and controlling growth, metabolism, and reproduction by regulating gene expression.It's a large, membrane-bound organelle, separated from the cytoplasm by the nuclear envelope, which contains pores for molecular traffic, and inside it holds chromatin, the nucleolus (for ribosome synthesis), and nucleoplasm.

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Key Components

• Nuclear Envelope: A double membrane with pores(nuclear pores) that control entry and exit of molecules like RNA and proteins.123
• Chromatin: The complex of DNA and proteins (histones) that forms chromosomes.123
• Nucleolus: A dense structure where ribosomal RNA (rRNA) is synthesized and ribosomes are assembled.123
• Nucleoplasm: The jelly-like substance filling the nucleus.12

Main Functions

• Genetic Control: Stores and protects the cell's DNA.12
• Gene Expression: Site for DNA replication, transcription (making RNA from DNA), and RNA processing.12
• Protein Synthesis Regulation: Directs protein production by sending messenger RNA (mRNA) out to the cytoplasm.12

Variations

• Most cells have one nucleus, but some (like muscle cells) are multi-nucleated, while others (like mature red blood cells) lack one.123

Inductively coupled plasma (ICP) is a high-temperature, high-density source of ions and electrons used in analytical techniques such as ICP-OES and ICP-MS to perform elemental analysis of samples.A radio-frequency electric current in an induction coil creates an oscillating magnetic field, which heats and ionizes argon gas flowing through a quartz torch to form the plasma.This plasma is hot enough to atomize samples, making them suitable for elemental quantification by either measuring the light they emit (ICP-OES) or by identifying the ions with a mass spectrometer (ICP-MS).

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How Inductively Coupled Plasma Works (The ICP-OES Principle)

1. Sample Introduction:The sample is introduced into a stream of argon gas and aerosolized.12
2. Plasma Formation:The aerosolized sample then enters a quartz torch within a radio-frequency induction coil.12
3. Atomization and Excitation:The high temperature of the argon plasma (around 6,000-10,000 K) completely vaporizes the sample, breaks it down into individual atoms, and then excites these atoms to higher energy levels.123456
4. Light Emission:As the excited electrons return to their lower energy states, they emit light at specific wavelengths characteristic of the elements present in the sample.12
5. Detection:An optical emission spectrometer analyzes this emitted light, and the intensity at each wavelength is proportional to the concentration of the corresponding element in the sample.12

ICP-MS (Inductively Coupled Plasma - Mass Spectrometry)12

• Similar to ICP-OES, but instead of detecting light, it uses a mass spectrometer to measure the ions directly.
• It excels at detecting trace elements at very low concentrations.

Uses of ICP

Inductively coupled plasma is a versatile tool used across many industries for elemental analysis, including:123456789101112131415

• Environmental monitoring:Analyzing water, soil, and air for contaminants.
• Pharmaceutical analysis:Ensuring drug purity and safety.
• Food and beverage analysis:Testing for heavy metals and essential nutrients.
• Geochemical analysis:Studying the elemental composition of rocks and minerals.
• Clinical research:Measuring elements in biological samples.

Cytotoxic T cells, also called killer T cells or CD8+ cells , are a type of immune cell that identifies and kills infected cells, cancer cells, and foreign cells . They accomplish this by releasing proteins like perforin and granzymes to trigger cell death, or by using the Fas ligand pathway, all of which are potent and require direct cell-to-cell contact. These cells are a crucial part of the adaptive immune system, but can also cause autoimmune diseases and graft rejection.12345

How they work

• Recognizing the target: Cytotoxic T cells recognize abnormal cells (like those infected by a virus) because these cells present foreign or abnormal fragments on their surface through major histocompatibility complex (MHC) molecules.
• Direct killing mechanisms:
  • Perforin and Granzymes: Upon recognizing a target cell, cytotoxic T cells release granules containing perforin, which creates pores in the target cell's membrane. This allows granzymes to enter and trigger apoptosis, or programmed cell death.
  • Fas Ligand (FasL): The T cell can also express Fas ligand on its surface. When this binds to the Fas receptor on a target cell, it sends a signal that initiates the cell's self-destruction process through a different pathway.
• Indirect killing: In addition to direct cell killing, cytotoxic T cells can secrete cytokines, such as TNFα, that can induce apoptosis in neighboring tumor cells that have the corresponding receptor.12345

Role in the body

• Fighting infections: They are essential for clearing viral infections and intracellular pathogens.
• Controlling cancer: They can identify and kill cancer cells, and are a focus of cancer immunotherapy.
• Autoimmunity and rejection: Because they are so potent, they can target the body's own tissues, leading to autoimmune diseases, or attack transplanted organs, causing graft rejection.1234